Free Estrogens in Dog Plasma During the Estrous Cycle and Pregnancy. ∗ †

Summary

Solvent partitioning, paper and thin-layer chromatography, and fluorometry were employed to isolate, identify and quantitate the free estrone, estradiol-17α, estradiol-17β, estriol and 16-epiestriol in dog plasma during the estrous cycle and pregnancy. There was a continuous decline in both individual and combined estrogen concentrations from early proestrus to late estrus. Throughout pregnancy the levels of estradiol-17α and 16-epiestriol remained fairly constant. Estrone and estradiol-17β attained peak levels at 3–4 weeks and declined thereafter. Estriol was the major metabolite and by the last week of pregnancy showed a 43% increase over the initial level. All of the estrogens except estradiol-17α rose substantially during the first week post-partum.