AJP - Endocrinology and Metabolism, Vol 263, Issue 1 E23-E27, Copyright © 1992 by American Physiological Society
Free and sulfoconjugated catecholamine responses at birth in newborn sheep
K. Oyama, J. Padbury, A. Martinez, B. Chappell, H. Stein, L. Blount and E. Buhl
Perinatal Research Laboratories, University of California, Los Angeles Harbor Medical Center, Torrance 90509.
There have been little data on catecholamine sulfoconjugation in developing
animals or humans. We studied the differences in free and sulfoconjugated
catecholamines at birth in newborn sheep. Baseline concentrations of
sulfoconjugated norepinephrine and epinephrine were the predominant form of
circulating catecholamine, representing 77 +/- 4 and 65 +/- 12% of total
circulating catecholamines, respectively. At birth the free epinephrine
concentration increased 10-fold (49 +/- 27 to 653 +/- 21 pg/ml,
respectively), and plasma free norepinephrine concentration rose 4-fold
(307 +/- 92 to 1,178 +/- 389 pg/ml). In contrast, there was only a
transient twofold increase in the sulfoconjugated epinephrine. There was no
increase in the sulfoconjugated form of norepinephrine. These data
demonstrate that, while the near-term newborn sheep has a well-developed
mechanism for sulfoconjugation of circulating catecholamines, this does not
occur rapidly. During the logarithmic increases of circulating
catecholamines at birth, there are not commensurate increases in the
concentration of sulfoconjugated norepinephrine or epinephrine. Thus
sulfoconjugation does not appear to represent a significant mechanism for
inactivation of the high circulating levels of catecholamines seen at
birth.
