title: Interaction of thyroid hormone and sex steroids at the rabbit reticulocyte membrane in vitro: control by 17 beta-estradiol and testosterone of thyroid hormone-responsive Ca2+-ATPase activity.
abstract: Physiological concentrations (10(-10) M) of L-thyroxine and triiodo-L-thyronine were found in vitro to enhance Ca2+-ATPase activity in reticulocyte-enriched red cell membranes from female rabbits and to inhibit this enzyme in the male reticulocyte. Cross-incubation experiments with reticulocyte-enriched red cells and plasma from the opposite sex demonstrated that this sex-specific membrane response to thyroid hormone was transferable by plasma. Similar experiments with intact reticulocytes exposed to physiological concentrations (10(-11) M) of testosterone and 17 beta-estradiol indicated that the plasma factors were the sex steroids. That is, incubation in vitro with testosterone converted female-source reticulocytes to male-type responsiveness to thyroid hormone (inhibition of Ca2+-ATPase activity); incubation with estradiol converted male-source reticulocyte-enriched red cells to female-type responsiveness (stimulation by iodothyronines of membrane Ca2+-ATPase activity). Similar results were obtained when reticulocyte ghosts were incubated with testosterone and 17 beta-estradiol prior to determination of membrane enzyme activity. Etiocholanolone (5 beta-androstan-3 alpha-ol-17-one) and testosterone were equipotent, but 5 alpha-dihydrotestosterone had little activity in this system. Estrone and estradiol were equipotent, but estriol had no permissive effect on the stimulation by iodothyronine of reticulocyte membrane Ca2+-ATPase activity. Expression of thyroid hormone action in vitro on Ca2+-ATPase activity in the rabbit reticulocyte is determined at the membrane level by testosterone and estrogen. The structure-activity relationships of the sex steroids for this membrane action are different than those reported for nuclear actions of the steroids.
mesh_terms: D000818:Animals; D000252:Calcium-Transporting ATPases / Q000097:blood*; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000201:enzymology; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D008297:Male; D011817:Rabbits; D012156:Reticulocytes / Q000187:drug effects / Q000201:enzymology*; D012737:Sex Factors; D013739:Testosterone / Q000494:pharmacology*; D013963:Thyroid Hormones / Q000494:pharmacology*
chemical_list: D013963:Thyroid Hormones; D013739:Testosterone; D004958:Estradiol; D000252:Calcium-Transporting ATPases