AJP - Regulatory, Integrative and Comparative Physiology, Vol 244, Issue 1 31-R35, Copyright © 1983 by American Physiological Society
Relationships between maternal hormones and weight of newborn sheep
D. Caton, P. S. Kalra and C. J. Wilcox
Intact and ovariectomized mixed-breed sheep were studied in chronic
experiments during the last weeks of pregnancy. Measurements were made of
the rate of uterine blood flow (ml/min and ml X min-1 X kg-1, combined
weight of fetus, uterus, and placenta) and of arterial and uterine venous
concentrations of progestagens, estrone, and estradiol. The birth weight of
the lamb was directly related to mean maternal concentrations of estrone
and estradiol and to the rate of progestagen release by the uterus and its
contents (ng X ml-1 X kg-1), calculated by taking the product of the rate
of blood flow and the arteriovenous progestagen difference. Ovariectomy
altered the relationship between birth weight and progestagen release. Data
suggest that rates of progestagen release both by the fetoplacental unit
and by the ovary are proportional to the birth weight of the lamb.
