Binding of the contraceptive steroids medroxyprogesterone acetate and ethynyloestradiol in blood of various species

• Published in: Journal of steroid biochemistry Vol. 14; no. 5; pp. 493 - 498
• Main Authors: Akpoviroro, J.O., Mangalam, M., Jenkins, N., Fotherby, K.
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 01.05.1981
• Subjects: Animals; Blood Proteins - metabolism; Dogs; Ethinyl Estradiol - blood; Guinea Pigs; Humans; Macaca mulatta; Medroxyprogesterone - analogs & derivatives; Medroxyprogesterone - blood; Medroxyprogesterone Acetate; Papio; Population; Protein Binding; Rabbits; Rats; Species Specificity; Hemic System; Ethinyl Estradiol > analysis; Estrogens; Contraceptive Agents, Estrogen > analysis; Biology; Contraception; Family Planning; Research Methodology; Medroxyprogesterone Acetate > analysis; Contraceptive Agents, Progestin > analysis; Clinical Research; Hematological Effects; Contraceptive Agents, Female > analysis; Contraceptive Agents > analysis; Physiology; Animals, Laboratory; Plasma Protein Binding Capacity
• ISSN: 0022-4731
• DOI: 10.1016/0022-4731(81)90362-9

The binding of medroxyprogesterone acetate (MPA) and ethynyloestradiol to plasma from baboons, monkeys, dogs, rabbits, guinea-pigs and rats was compared to that in the human. For MPA, binding in the rabbit was significantly higher, and in the guinea-pig significantly lower, than that in the other species, which showed about 80% binding of the steroid. Polyacrylamide gel electrophoresis (PAGE) showed that binding occurred only to albumin. More than 90% of ethynyloestradiol was bound by plasma from all species and in all the species except dog and guinea-pig, binding occurred only to albumin. In the latter two species there was some evidence for ethynyloestradiol binding in the globulin fraction but no binding in any species appeared to occur to SHBG. The steroid-albumin complexes showed variations in stability on PAGE. Variations in stability and in apparent association constants of the steroid-albumin complexes may produce variations in the biological activity of the steroids in the different species.