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1 Oral and Maxillofacial Surgery, Eastman Dental Institute, London WC1X 8LD; and 2 Department of Anatomy and Developmental Biology, University College London, London WC1E 6BT, United Kingdom
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ABSTRACT |
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 TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES
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We examined the effects of
HCO3
and CO2 acidosis on
osteoclast-mediated Ca2+ release from 3-day cultures of
neonatal mouse calvaria. Ca2+ release was minimal above pH
7.2 in control cultures but was stimulated strongly by the addition of
small amounts of H+ to culture medium
(HCO3 acidosis). For example, addition of 4 meq/l
H+ reduced pH from 7.12 to 7.03 and increased
Ca2+ release 3.8-fold. The largest stimulatory effects (8- to 11-fold), observed with 15-16 meq/l added H+, were
comparable to the maximal Ca2+ release elicited by
1,25-dihydroxyvitamin D3
[1,25(OH)2D3; 10 nM], parathyroid hormone (10 nM), or prostaglandin E2 (1 µM); the action of these
osteolytic agents was attenuated strongly when ambient pH was increased
from ~7.1 to ~7.3. CO2 acidosis was a less effective
stimulator of Ca2+ release than HCO3
acidosis over a similar pH range. Ca2+ release stimulated
by HCO3 acidosis was almost completely blocked by
salmon calcitonin (20 ng/ml), implying osteoclast involvement. In whole
mount preparations of control half-calvaria, ~400 inactive
osteoclast-like multinucleate cells were present; in calvaria exposed
to HCO3 acidosis and to the other osteolytic agents
studied, extensive osteoclastic resorption, with perforation of bones,
was visible. HCO3 acidosis, however, reduced numbers
of osteoclast-like cells by ~50%, whereas
1,25(OH)2D3 treatment caused increases of
~75%. The results suggest that HCO3 acidosis
stimulates resorption by activating mature osteoclasts already present
in calvarial bones, rather than by inducing formation of new
osteoclasts, and provide further support for the critical role of
acid-base balance in controlling osteoclast function.
calcium release; carbon dioxide; bicarbonate ion; acid-base balance; osteolysis
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INTRODUCTION |
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TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES
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THE SKELETON CONTAINS a massive reserve of base that is available as a "fail-safe" mechanism to buffer protons if the kidney and lungs are unable to maintain acid-base balance within narrow physiological limits (8, 15). The deleterious effects of systemic acidosis on the skeleton have been recognized at least since the early part of this century (5, 18). More recent in vivo studies have suggested that the bone loss associated with acidosis is not due to passive physicochemical processes but involves enhanced osteoclastic resorption (9, 22).
Experiments with disaggregated rat osteoclasts cultured on cortical
bone or dentine wafers provided the first direct evidence for the
stimulatory action of extracellular protons on cell-mediated bone
resorption. Resorption pit formation by rat osteoclasts in culture
media buffered nonphysiologically, with the use of HEPES only, was
activated by progressive acidification from pH 7.4 to 6.8 (3). Cultured osteoclasts are also stimulated to resorb in
physiologically buffered media when pH is reduced either by decreasing
HCO3 concentration or by increasing
PCO2 (2). Recent work has shown that rat osteoclasts are particularly sensitive to extracellular pH in
the range 7.2-7.0, such that shifts of <0.1 unit are sufficient to cause changes of severalfold in pit formation (6).
Experiments with cultured mouse calvaria showed that calcium
efflux from bones was stimulated much more strongly when extracellular pH was reduced by decreasing HCO3 concentration
(metabolic acidosis) than by increasing PCO2
(respiratory acidosis) (11, 12). The aims of the present
study were 1) to investigate the effects of small
extracellular pH changes resulting from HCO3 and
CO2 acidosis on osteoclastic resorption in cultured
calvaria; 2) to compare the effects of acidosis on calvarial
resorption with those of "classical" osteolytic agents and to
determine whether the action of these agents was dependent on ambient
acidification; and 3) to investigate whether acidosis
stimulates resorption by activating mature osteoclasts already present
in calvarial bones or by inducing formation of new osteoclasts.
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MATERIALS AND METHODS |
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TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES
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Reagents. 1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] was kindly provided by Dr K. W. Colston (St. George's Hospital Medical School, London, UK). BWA 70C, a 5-lipoxygenase inhibitor of the iron ligand class, containing the hydroxamic acid chelating group, was a gift of the Wellcome Foundation (Beckenham, Kent, UK). MK 886, a selective inhibitor of the 5-lipoxygenase-activating protein (FLAP), was donated by Merck Frosst (Kirkland, QC, Canada). Other reagents, unless specified, were purchased from Sigma (Poole, Dorset, UK).
Mouse calvarial bone resorption assay.
The method, which measures bone resorption as Ca2+ release
from neonatal mouse calvaria, was similar to that described in detail by Meghji et al. (24). Briefly, 5-day-old MF1 mice were
killed by cervical dislocation. The frontoparietal bones were removed and trimmed of any adhering connective tissue and interparietal bone,
with care being taken not to damage the periosteum. Dissected calvaria
were pooled, washed free of blood and adherent brain tissue in Hanks'
balanced salt solution, and then divided along the sagittal suture.
Half-calvaria were cultured individually on 1-cm2 stainless
steel grids (Minimesh, FDP quality, Expanded Metal, West Hartlepool,
UK) in 6-well plates with 1.5 ml of BGJ medium, 5%
heat-inactivated fetal calf serum, 100 U/ml penicillin, and 100 µg/ml
streptomycin (ICN Biomedicals, Basingstoke, Hants, UK) at the
air-liquid interface in a humidified CO2 incubator. After an initial 24-h preincubation period, the medium was removed and replaced with control or test media. Prostaglandin E2
(PGE2), 1,25(OH)2D3, indomethacin,
BWA 70C, and MK 886 were dissolved in ethanol vehicle for use; the
final concentration of ethanol in cultures did not exceed 1:500. Each
experimental group consisted of five individual cultures. Included in
each experiment were groups of half-calvaria that had been killed by
three cycles of freeze-thawing with liquid nitrogen. The cultures were
then incubated for 72 h without further medium changes and without
the incubator door being opened, so as to ensure constant
CO2 levels and minimize pH fluctuations. Culture medium
acidification was achieved either by adding small amounts of
concentrated HCl to culture medium as described by Murrills et al.
(31), resulting in decreased HCO3
concentration (metabolic acidosis) or by increasing incubator CO2 tension (respiratory acidosis).
Whole mount histology. After fixation/decalcification with 95% ethanol-5% glacial acetic acid, calvaria were stained for tartrate-resistant acid phosphatase (TRAP) (20, 23) by means of a Sigma kit 387-A and were mounted in melted glycerol jelly. The numbers of TRAP-positive multinucleated osteoclasts (two or more nuclei) were assessed blind on coded samples by means of transmitted light microscopy.
Statistics. Statistical comparisons, where appropriate, were made by one-way analysis of variance, with the use of Bonferroni's correction for multiple comparisons. Representative data are presented as means ± SE for 5 replicates. Results are shown for representative experiments that were each repeated at least three times.
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RESULTS |
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TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES
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Effect of HCO3 acidosis on calvarial resorption.
Basal levels of Ca2+ release in nonacidified control bones
(pH 7.20-7.25) were very low after 3 days of culture.
Acidification of culture medium by addition of small amounts of
H+ as HCl resulted in a steep increase in Ca2+
release from live bones. For example, decreasing the pH of the culture
medium from 7.21 (control) to 7.17 by addition of 3 meq/l H+ reduced HCO3 concentration from 13.2 to 12.2 mmol/l, resulting in a 2.8-fold increase in Ca2+
release, and decreasing the pH to 6.94 by addition of 15 meq/l H+ reduced HCO3 concentration to 7.1 mmol/l, causing an 8.3-fold stimulation of Ca2+ release. In
contrast, in bones killed by freeze-thawing, there was a marked influx
of Ca2+, evidenced by a decrease in culture medium
Ca2+ concentration; the magnitude of this influx was
slightly reduced with progressive acidification (Fig.
1).
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Effect of CO2 acidosis.
When culture medium was acidified from 7.12 to 6.90 by increasing
incubator PCO2 from 54.5 to 87.2 mmHg, only a
small, nonsignificant increase in Ca2+ release from
calvaria was observed after 3 days of culture. The stimulation of
Ca2+ release resulting from CO2 acidosis was
markedly lower than that elicited by HCO3 acidosis at
comparable pH values. However, further acidification to pH 6.81 by
increasing PCO2 to 108.5 mmHg resulted in a
5.3-fold stimulation of Ca2+ release compared with control.
This stimulation occurred in the face of an increase in
HCO3 concentration from 15.8 to 22.5 mM (Fig.
2).
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Effects of inhibitors.
HCO3 acidosis-stimulated Ca2+ release
(resulting from addition of 15 meq/l H+) was completely
blocked by salmon calcitonin (20 ng/ml; Fig. 3). Thus Ca2+ release
stimulated by HCO3 acidosis was due to osteoclastic
resorption. Ca2+ release resulting from severe
CO2 acidosis was also blocked by salmon calcitonin (20 ng/ml; data not shown). HCO3 acidosis-stimulated
Ca2+ release was additionally completely blocked by the
cyclooxygenase inhibitors indomethacin (Fig.
4) and ibuprofen (data not shown) and was
inhibited by the 5-lipoxygenase inhibitors, BWA 70C (Fig. 5A) and MK 886 (Fig.
5B), suggesting that the effect may be mediated by both
prostaglandins and leukotrienes.
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Effects of "classical" resorption stimulators.
The maximal effects of the osteolytic agents
1,25(OH)2D3 (10 nM), bovine parathyroid
hormone-(1-34) (PTH, 20 ng/ml) and PGE2 (1 µM) on Ca2+ release from 3-day calvarial cultures were
similar and were equivalent in magnitude to the effect of
HCO3 acidosis at pH 6.94 (15 meq/l added
H+; Fig. 6). In most
experiments, PTH, 1,25(OH)2D3, and
PGE2 treatments themselves resulted in slight acidification
of culture medium.
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as NaOH increased final medium pH from ~7.1 in
control cultures to ~7.3, resulting in marked attenuation of
Ca2+ release in all treatment groups (Fig.
7). Addition of equivalent amounts of
Na+ as NaCl to culture medium was without effect on bone
resorption. In the case of PGE2-stimulated bones,
increasing pH from 7.12 to 7.33 reduced resorption by 80%.
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Histology (TRAP staining) and cell counting.
In whole mount preparations of half-calvaria cultured in control medium
for 3 days and then stained to demonstrate tartrate-resistant acid
phosphatase, ~200-400 inactive TRAP-positive osteoclast-like multinucleate cells were typically present; resorption cavities visualized by the TRAP staining were small and relatively inactive (Figs. 8A and 9). The
appearance of freshly isolated bones (i.e., not cultured) was similar.
In calvaria exposed to HCO3 acidosis (
12 meq/l
H+), extensive osteoclastic resorption cavities, with
characteristic scalloped edges, were evident (Fig. 8B);
resorption was sometimes sufficiently aggressive to cause complete
perforation of bones. In bones exposed to severe CO2
acidosis (108.5 mmHg) at pH 6.82, osteoclasts in scalloped resorption
bays were also clearly evident (Fig. 8C). Extensive
resorption cavities were also observed in bones treated with 10 nM
1,25(OH)2D3 (Fig. 8D), 20 ng/ml
PTH-(1-34), or 1 µM PGE2. However, cell
counts revealed that HCO3 acidosis reduced the
numbers of osteoclast-like cells by ~50% compared with controls,
whereas 1,25(OH)2D3 treatment caused increases of ~75% (Fig. 9).
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DISCUSSION |
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TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES
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The present study correlates Ca2+ release data with
histological evidence to demonstrate that osteoclastic resorption in
cultured mouse calvarial bones is extremely sensitive to activation by HCO3 acidosis, an effect which can cause bone
destruction equivalent to the maximal osteolysis produced by agents
such as 1,25(OH)2D3, PTH, or PGE2.
Furthermore, our results show that the action of these classical
osteolytic agents is attenuated markedly by slight alkalinization. We
also found that severe CO2 acidosis resulted in increased
osteoclastic resorption.
Three separate lines of evidence indicate that net Ca2+
release into the culture medium from mouse calvarial bones stimulated by HCO3 acidosis is almost entirely the result of
osteoclast activity. First, salmon calcitonin (20 ng/ml) completely
blocked the Ca2+ release from live bones stimulated by
HCO3 acidosis. Second, in bones killed by
freeze-thawing, HCO3 acidosis exerted only a minimal
effect, i.e., a slight reduction of the net Ca2+ influx
that was always observed. Although such dead bones do not provide a
perfect control because freeze-thawing may render the cellular lining
of calvarial surfaces more "leaky," our data suggest that the
influence of HCO3 acidosis on physicochemical
Ca2+ exchange was small, even at large acid loads. These
results are in essential agreement with the earlier findings of
Goldhaber and Rabadjija (17). Third, in calvaria exposed
to HCO3 acidosis (12 meq/l H+),
extensive osteoclastic resorption cavities were present; such cavities
were absent in calcitonin-treated bones.
Our findings show that bone resorption in cultured mouse calvaria may
be more sensitive to small pH changes than was previously appreciated.
Ca2+ release was minimal above pH 7.2 in control cultures
but was stimulated strongly by the addition of small amounts of
H+ (i.e., HCO3 acidosis) to culture
medium. Figure 2 shows that addition of 4 meq/l H+ reduced
pH from 7.12 to 7.03 but increased Ca2+ release 3.8-fold;
an 11-fold increase was observed with 16 meq/l added H+.
The steep responses to HCO3 acidosis evident in Figs.
1 and 2 resemble closely the acid-activation curve for resorption pit
formation by cultured rat osteoclasts in which resorption is
essentially "switched off" above pH 7.2 and stimulated
maximally at pH ~6.9 (6, 31). Osteoclasts derived from
chick long bones (4, 28), human osteoclastoma tissue
(19), or long-term mouse marrow cultures (29)
show remarkably similar responses to extracellular pH changes. Taken together, these observations suggest that the local pH in the microenvironment of osteoclasts in cultured mouse parietal bones is
close to that of the tissue culture medium and thus considerably lower
than that of blood pH (~7.40).
We also demonstrated that CO2 acidosis is a less effective
stimulator of Ca2+ release from calvarial bones than
HCO3 acidosis over a similar pH range, a result that
is in good agreement with data from the 45Ca2+
flux experiments of Bushinsky and colleagues (11, 12). One partial explanation for the smaller stimulatory effect of
CO2 acidosis may be that hypercapnia promotes deposition of
Ca2+, as carbonates, on bone surfaces (11).
Nevertheless, our own results show that resorption is activated quite
strongly by severe CO2 acidosis at low pH
(PCO2 = 108.5 mmHg; pH = 6.81). It
may be that, when PCO2 is increased, the "set
point" at which resorption begins to be acid activated is shifted to
lower pH values. It is also noteworthy that the striking stimulation of
bone resorption caused by severe CO2 acidosis occurred
despite an increase in HCO3 concentration (22.5 mM
compared with control value of 15.8 mM). This result suggests that, in
the main, it is the increased H+ concentration that is
ultimately responsible for acidosis-stimulated osteclastic bone
resorption. Experiments with cultured osteoclasts have not shown
clear differences between the effects of CO2 and HCO3 acidosis in stimulating pit formation (Ref.
2; M. Morrison and T. R. Arnett, unpublished data).
The reasons for this discrepancy are unknown. In vivo,
HCO3 acidosis is associated with bone loss (reviewed
in Ref. 5). In thyroparathyroidectomized rats, acute
HCO3 acidosis induced by acid feeding results in a
striking hypercalcemia that is prevented by calcitonin or colchicine,
implying osteoclast involvement (22). The effects of
CO2 acidosis in vivo are less well investigated; however, a
recent study (32) reported that hormone replacement
therapy causes a respiratory alkalosis in normal postmenopausal women
and that changes in blood pH were inversely correlated with those in
urinary excretion of hydroxyproline, an index of bone resorption.
The behavior of the calvarial system in response to acid stimulation
also differs from that of cultured osteoclasts in another key respect.
We found that resorption stimulated by HCO3 acidosis
could be blocked by the cyclooxygenase inhibitors indomethacin and
ibuprofen, in line with earlier findings (17, 33) and suggesting a requirement for endogenous prostaglandin synthesis. In
contrast, resorption pit formation by cultured osteoclasts is
stimulated by cyclooxygenase inhibitors (26, 27) and is inhibited by prostaglandins (4, 13). Our observation that HCO3 acidosis-activated resorption was additionally
attenuated by two mechanistically distinct inhibitors of the
5-lipoxygenase pathway suggests that leukotrienes, which stimulate bone
resorption in a number of systems (16, 25), are also
involved in mediating the effect.
In this study, we correlated a biochemical index of calvarial bone
resorption (Ca2+ release) with quantitative histological
analysis of the same bones. Surprisingly, perhaps, this approach has
not been used before. The simple whole mount histological technique we
used was first described by Marshall and colleagues (20,
23), who reported that ~200 multinucleate, TRAP-positive
osteoclasts were visible in single parietal bones of 4-day-old mice
before being placed in culture; our own data for control bones agree
well with these values. In calvaria exposed to HCO3
acidosis, extensive osteoclastic resorption cavities were evident, but
TRAP-positive osteoclast numbers were reduced consistently. Whether
this change in osteoclast numbers reflects reductions in osteoclast
survival, formation, or both, is uncertain. Cell culture experiments
have shown that osteoclast formation in 10-day mouse marrow cultures is
inhibited at pH 6.9-7.0 (29); however, survival of
mature osteoclasts in this pH range appears unimpaired (3, 6,
31). Thus the impressive resorption cavities seen in calvaria
exposed to acidosis may reflect mainly the activation of preexisting
quiescent osteoclasts rather than the formation of new
osteoclasts. However, the possibility cannot be excluded that acidosis
rapidly stimulates the formation of new osteoclasts, which are then
immediately activated, alongside increased apoptosis of preexisting
quiescent osteoclasts.
In contrast, the osteolytic effects of
1,25(OH)2D3 appeared to be related, at least in
part, to increases in TRAP-positive osteoclast numbers, reflecting the
stimulatory action of this hormone on osteoclast formation in long-term
marrow cultures. Ca2+ release in
1,25(OH)2D3-treated cultures was similar to
that in cultures exposed to HCO3 acidosis, but
resorption on a per cell basis was ~3.5-fold lower, based on the cell
counts shown in Fig. 9. Interestingly, cultures treated with
1,25(OH)2D3, PTH, or PGE2 generally
exhibited slight acidification compared with controls. Similar effects
of PTH have been described previously (10, 14); this is
probably due to a stimulation of H+ efflux from
osteoblastic target cells (7, 35). We have recently found
that 1,25(OH)2D3 also stimulates extracellular
acidification by cultured primary osteoblast-like cells derived from
rodent calvaria (34). Other bone-resorbing agents reported
to stimulate H+ efflux from osteoblast-like cells include
insulin-like growth factor I (35), interleukin-1 (1,
34) and ATP (21). Obviously, such acidification
could account for some of the osteolytic action of these agents
(5, 30).
In conclusion, our findings indicate that the modulation of osteoclast activity by small pH changes is a key determinant of bone resorption in mouse calvarial cultures. Similar responses to extracellular acidification have been observed in all bone resorption systems examined to date. The great sensitivity of osteoclasts to extracellular protons may have evolved in vertebrates as a last line of defense against systemic acidosis.
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ACKNOWLEDGEMENTS |
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We are grateful to the Arthritis Research Campaign for support. M. S. Morrison was the recipient of a Medical Research Council PhD studentship.
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FOOTNOTES |
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Address for reprint requests and other correspondence: T. R. Arnett, Dept. of Anatomy and Developmental Biology, University College London, Gower St., London WC1E 6BT, UK (E-mail: t.arnett{at}ucl.ac.uk).
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Received 12 May 2000; accepted in final form 6 September 2000.
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REFERENCES |
|---|
|
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES
|
|---|
1.
Aisa, MC,
Rahman S,
Senin U,
Oyajobi OB,
Maggio D,
and
Russell RGG
IL-1
-stimulated acid secretion by human osteoblast-like cells and human osteosarcoma cells MG-63.
J Bone Miner Res
10:
S421,
1995.
2.
Arnett, TR,
Boyde A,
Jones SJ,
and
Taylor ML.
Effects of medium acidification by alteration of carbon dioxide or bicarbonate concentrations on the resorptive activity of rat osteoclasts.
J Bone Miner Res
9:
375-379,
1994[Web of Science][Medline].
3.
Arnett, TR,
and
Dempster DW.
Effect of pH on bone resorption by rat osteoclasts in vitro.
Endocrinology
119:
119-124,
1986
4.
Arnett, TR,
and
Dempster DW.
A comparative study of disaggregated chick and rat osteoclasts in vitro: effect of calcitonin and prostaglandins.
Endocrinology
120:
602-608,
1987
5.
Arnett, TR,
and
Dempster DW.
Perspectives: protons and osteoclasts.
J Bone Miner Res
5:
1099-1103,
1990[Web of Science][Medline].
6.
Arnett, TR,
and
Spowage M.
Modulation of the resorptive activity of rat osteoclasts by small changes in extracellular pH near the physiological range.
Bone
18:
277-279,
1996[Medline].
7.
Barrett, MG,
Belinsky GS,
and
Tashjian AH, Jr.
A new action of parathyroid hormone: receptor-mediated stimulation of extracellular acidification in human osteoblast-like SaOS-2 cells.
J Biol Chem
272:
26346-26353,
1997
8.
Barzel, US.
The skeleton as an ion-exchange system
implications for the role of acid-base imbalance in the genesis of osteoporosis.
J Bone Miner Res
10:
1431-1436,
1995[Web of Science][Medline].
9.
Barzel, US,
and
Jowsey J.
The effects of chronic acid and alkali administration on bone turnover in adult rats.
Clin Sci (Colch)
36:
517-524,
1969[Web of Science][Medline].
10.
Belinsky, GS,
and
Tashjian AH, Jr.
Direct measurement of hormone-induced acidification in intact bone.
J Bone Miner Res
15:
550-556,
2000[Medline].
11.
Bushinsky, DA.
Stimulated osteoclastic and suppressed osteoblastic activity in metabolic but not respiratory acidosis.
Am J Physiol Cell Physiol
268:
C80-C88,
1995
12.
Bushinsky, DA,
Sessler NE,
and
Krieger NS.
Greater unidirectional calcium efflux from bone during metabolic, compared with respiratory, acidosis.
Am J Physiol Renal Fluid Electrolyte Physiol
262:
F425-F431,
1992
13.
Chambers, TJ,
Fuller K,
McSheehy PM,
and
Pringle JA.
The effects of calcium regulating hormones on bone resorption by isolated human osteoclastoma cells.
J Pathol
145:
297-305,
1985[Medline].
14.
Felix, R,
Neuman WF,
and
Fleisch H.
Aerobic glycolysis in bone: lactic acid production by rat calvaria cells in culture.
Am J Physiol Cell Physiol
234:
C51-C55,
1978
15.
Frassetto, L,
and
Sebastian A.
Age and systemic acid-base equilibrium: analysis of published data.
J Gerontol
51A:
B91-B99,
1996[Web of Science].
16.
Garcia, C,
Boyce BF,
Gilles J,
Dallas M,
Qiao M,
Mundy GR,
and
Bonewald LF.
Leukotriene B4 stimulates osteoclastic bone resorption both in vitro and in vivo.
J Bone Miner Res
11:
1619-1627,
1996[Web of Science][Medline].
17.
Goldhaber, P,
and
Rabadjija L.
H+ stimulation of cell-mediated bone resorption in tissue culture.
Am J Physiol Endocrinol Metab
253:
E90-E98,
1987
18.
Goto, K.
Mineral metabolism in experimental acidosis.
J Biol Chem
36:
355-376,
1918
19.
Hoebertz, A,
Nesbitt SA,
Horton MA,
and
Arnett TR.
Acid activation of osteoclasts derived from human osteoclastoma.
J Bone Miner Res
14:
1049,
1999.
20.
Holt, I,
and
Marshall MJ.
Integrin subunit 3 plays a crucial role in the movement of osteoclasts from the periosteum to the bone surface.
J Cell Physiol
175:
1-9,
1998[Medline].
21.
Kaplan, AD,
and
Dixon SJ.
Extracellular nucleotides act through P2 purinoceptors to modulate acid production by osteoblastic cells (Abstract).
J Bone Miner Res
11 (S1):
S385,
1996.
22.
Kraut, JA,
Mishler DR,
and
Kurokawa K.
Effect of colchicine and calcitonin on calcemic response to metabolic acidosis.
Kidney Int
25:
608-612,
1984[Web of Science][Medline].
23.
Marshall, MJ,
Holt I,
and
Davie MJW
The number of tartrate-resistant acid phosphatase-positive osteoclasts on neonatal mouse parietal bones is decreased when prostaglandin synthesis is inhibited and increased in response to prostaglandin E2, parathyroid hormone and 1,25-dihydroxyvitamin D3.
Calcif Tissue Int
56:
240-245,
1995[Medline].
24.
Meghji, S,
Hill PA,
and
Harris M.
Bone organ cultures.
In: Methods in Bone Biology, edited by Arnett TR,
and Henderson B. London, UK: Chapman and Hall, 1998, p. 106-126.
25.
Meghji, S,
Sandy JR,
Scutt AM,
Harvey W,
and
Harris M.
Stimulation of bone resorption by lipoxygenase metabolites of arachidonic acid.
Prostaglandins
36:
139-149,
1988[Web of Science][Medline].
26.
Morrison, MS,
and
Arnett TR.
Indomethacin and ibuprofen stimulate pit formation by rat osteoclasts (Abstract).
J Bone Miner Res
11:
1825,
1996.
27.
Morrison, MS,
and
Arnett TR.
The novel cyclooxygenase II inhibitor S-398 stimulates pit formation by rat osteoclasts (Abstract).
Bone
20:
111S,
1997.
28.
Morrison, MS,
and
Arnett TR.
Effect of extracellular pH on resorption pit formation by chick osteoclasts (Abstract).
J Bone Miner Res
12:
S290,
1997.
29.
Morrison, MS,
and
Arnett TR.
pH effects on osteoclast formation and activation (Abstract).
Bone
22:
30S,
1998.
30.
Morrison, MS,
Turin L,
King BF,
Burnstock G,
and
Arnett TR.
ATP is a potent stimulator of the activation and formation of rodent osteoclasts.
J Physiol (Lond)
511:
495-500,
1998
31.
Murrills, RJ,
Dempster DW,
and
Arnett TR.
Isolation and culture of osteoclasts and osteoclast resorption assays.
In: Methods in Bone Biology, edited by Arnett TR,
and Henderson B. London, UK: Chapman and Hall, 1998, p. 64-105.
32.
Orr-Walker, BJ,
Horne AM,
Evans MC,
Grey AB,
Murray MAF,
McNeil AR,
and
Reid IR.
Hormone replacement therapy causes a respiratory alkalosis in normal postmenopausal women.
J Clin Endocrinol Metab
84:
1997-2001,
1999
33.
Rabadjija, L,
Brown EM,
Swartz SL,
Chen CJ,
and
Goldhaber P.
H+-stimulated release of prostaglandin E2 and cyclic adenosine 3',5'-monophosphoric acid and their relationship to bone resorption in neonatal mouse calvaria cultures.
Bone Miner
11:
295-304,
1990[Web of Science][Medline].
34.
Sankararajah, D,
Pollington C,
Hoebertz A,
Morrison MS,
and
Arnett TR.
1,25(OH)2D3 and interleukin-1 stimulate extracellular acidification by cultured osteoblast-like cells from rat calvaria (Abstract).
Bone
26:
10S,
2000.
35.
Santhanagopal, A,
and
Dixon SJ.
Insulin-like growth factor I rapidly enhances acid efflux from osteoblastic cells.
Am J Physiol Endocrinol Metab
277:
E423-E432,
1999
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). PCO2 was 36.3 mmHg. Values are means ± SE (n = 5).
Significantly different from nonacidified control: *P < 0.05; **P < 0.01; ***P < 0.001.
