AJP - Regulatory, Integrative and Comparative Physiology, Vol 259, Issue 1 21-R24, Copyright © 1990 by American Physiological Society

ARTICLES

Effect of human pregnancy on metabolic clearance rate of oxytocin

S. Thornton, J. M. Davison and P. H. Baylis
Department of Obstetrics and Gynaecology, Princess Mary Maternity Hospital, Newcastle upon Tyne, United Kingdom.

The metabolic clearance rate (MCR) of oxytocin (OT) was determined by use of constant infusion techniques to achieve low and high plasma OT concentrations in 10 women in late pregnancy and again 8-10 wk postpartum (mean plasma oxytocinase activity was 2.1 IU/ml plasma at term and less than 0.1 IU/ml plasma 8-10 wk postpartum). At the lower plasma OT concentrations (5.0 and 5.2 pg/ml, pregnant and postpartum, respectively) produced by infusion of 17.9 ng/min in pregnancy and 4.3 ng/min postpartum, mean MCR of OT was increased fourfold during pregnancy (5.7 +/- 0.6 and 1.3 +/- 0.1 l/min, pregnant and postpartum, respectively; P less than 0.001). At the higher plasma OT concentrations (8.0 and 8.0 pg/ml, pregnant and postpartum, respectively) produced by infusion of 35.7 ng/min in pregnancy and 8.5 ng/min postpartum, mean MCR of OT was likewise markedly increased during pregnancy compared with postpartum values (7.1 +/- 1.9 and 1.4 +/- 0.1 l/min, respectively; P less than 0.01). The MCR of OT was independent of plasma concentration (between 5 and 8 pg/ml) during pregnancy and in the postpartum period. It is concluded that the MCR of OT is increased markedly during human pregnancy. This may be due to concomitant increases in in vivo cystine aminopeptidase activity or other less specific pregnancy-associated metabolic changes.

This article has been cited by other articles:

				W. B. Kowalski, L. Diveky, R. Mehendale, M. Parsons, and L. Wilson Jr. Effect of pregnancy on the metabolic clearance rate and the volume of distribution of oxytocin in the baboon Am J Physiol Endocrinol Metab, May 1, 1998; 274(5): E791 - E795. [Abstract] [Full Text] [PDF]