AJP - Endocrinology and Metabolism, Vol 241, Issue 6 454-E459, Copyright © 1981 by American Physiological Society
Hormonal activation of ornithine decarboxylase in embryonic chick pelvic cartilage
W. M. Burch and H. E. Lebovitz
We assessed whether hormones and metabolic factors known to stimulate
anabolic processes in the embryonic chick pelvic cartilage would stimulate
ornithine decarboxylase (ODC) activity. In vitro organ culture of these
pelvic cartilages in time-course experiments with N(6)-monobutyryl cyclic
AMP (BtcAMP), insulin, and 5% rat serum demonstrated maximal stimulation of
ODC activity between 4 and 6 h with each factor. However, at 2 h insulin
and serum significantly stimulated ODC activity (P less than 0.05) and
BtcAMP did not. ODC was stimulated above control (100%) with the following
factors: parathyroid hormone (PTH) (555 +/- 15%), BtcAMP (324 +/- 34%),
1-methyl-3-isobutylxanthine (MIX) (223 +/- 6%), prostaglandin E1 (PGE1)
(227 +/- 15%), 3,3',5-triiodothyronine (T3) (184 +/- 22%), insulin (182 +/-
14%), multiplication-stimulating activity (MSA) (178 +/- 6%), 5% rat serum
(253 +/- 57%). THe increase in ODC activity seen with BtcAMP and insulin
was not due to a change in Km or a decreased rate of degradation of the
enzyme. Actinomycin D (1 microgram/ml) inhibited stimulation of ODC
activity by T3 and the cyclic AMP-mediated factors (PTH, BtcAMP, MIX,
PGE1), but had only minimal effects on ODC stimulation by insulin, MSA, or
serum. Amanitin inhibited both BtcAMP and T3 stimulation of ODC, but had no
effect on insulin stimulation of ODC. Thus, hormones and metabolic factors
known to stimulate anabolic processes in chick embryonic pelvic cartilage
also increase ODC activity through at least two mechanisms: transcriptional
(cyclic AMP-mediated and T3) and posttranscriptional (insulin, serum, MSA).
