Levels of circulating and urinary oestrogens during pregnancy in the marmoset monkey (Callithrix jacchus)

Abstract

The levels of immunoreactive estrone, estradiol-17.beta. and estriol in plasma and urine were measured during early, mid- and late pregnancy in the marmoset monkey. In plasma, unconjugated estrone remained < 2% of total (conjugated plus unconjugated) estrone throughout gestation, while unconjugated estradiol-17.beta. increased from 3% of the total value in early and mid-pregnancy to 35% in late pregnancy. The reversal in the unconjugated estrone:estradiol-17.beta. concentration ratio from early (12:1) to late (0.15:1) pregnancy occurred despite the continuing predominance of estrone in terms of total hormone. Total estriol was measurable but in relatively low concentrations. Estradiol conjugate was the predominant urinary estrogen metabolite measured at each state of pregnancy. The pattern of urinary estrone and estradiol-17.beta. reflected plasma levels of total hormone, rather than unconjugated hormone, showing no further increase after mid-pregnancy. In contrast, estriol increased throughout pregnancy and to a proportionately greater extent than estrone or estradiol-17.beta., but at lower absolute levels. High-pressure liquid chromatography of urine extract indicated the presence of considerable amounts of estrogen immunoreactivity not accounted for by estrone, estradiol-17.beta. and estriol as well as with a retention time similar to that of 16.alpha.-hydroxyestrone. Gas chromatography and mass spectroscopy provided further evidence to suggest that 16.alpha.-hydroxyestrone is an abundant urinary estrogen metabolite during pregnancy in the marmoset monkey.