The effects of membrane permeability and binding by human serum proteins on steroid influx into the rabbit uterus.
The effects of capillary membrane permeability and binding by human plasma proteins on the influxes of tritium-labeled steroids from the circulation into the uterus were measured in vivo in anesthetized rabbits with a tissue-sampling, single injection technique, and the results were compared with similar studies involving rats. Rabbits were used in this study because this species, unlike the rat, has a sex steroid-binding protein. The impact of capillary membrane permeability markedly varied with different steroids and did not completely parallel the lipid solubility of these compounds. The addition of plasma proteins to the injection vehicle had varied inhibitory effects on the in vivo extractions by the uterus. These in vivo extraction values could not be predicted from in vitro studies of steroid binding to plasma proteins and the results underscore the importance of performing in vivo studies so that we may have a better understanding of the bioavailability of steroids to tissues.
Steingold
K A
KA
Department of Obstetrics and Gynecology, University of California Los Angeles School of Medicine 90024.
Pardridge
W M
WM
Judd
H L
HL
Chaudhuri
G
G
D000818:Animals; D001798:Blood Proteins / Q000493:pharmacokinetics*; D002199:Capillary Permeability / Q000187:drug effects*; D003345:Corticosterone / Q000378:metabolism*; D005260:Female; D012739:Gonadal Steroid Hormones / Q000378:metabolism*; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D011485:Protein Binding; D011817:Rabbits; D051381:Rats; D014599:Uterus / Q000378:metabolism*
D001798:Blood Proteins; D012739:Gonadal Steroid Hormones; D003345:Corticosterone; D006854:Hydrocortisone