Type I receptors in parotid, colon, and pituitary are aldosterone selective in vivo.
Previous in vivo studies have demonstrated that type I receptors in the rat kidney are aldosterone selective, whereas those in the hippocampus do not appear to discriminate between aldosterone and corticosterone. We have injected mature rats with [3H]aldosterone or [3H]corticosterone plus 100-fold excess of RU 28362, with or without unlabeled aldosterone or corticosterone, and compared type I receptor occupancy in two classic mineralocorticoid target tissues (parotid and colon) and in the pituitary. Mature rats were killed 10-180 min after tracer administration; [3H]aldosterone was well taken up and retained in all tissues, whereas [3H]corticosterone was significantly retained only in the pituitary 10 min after tracer administration. To assess a possible role for corticosterone-binding globulin (CBG) in conferring aldosterone specificity on type I receptors, 10-day-old rats (with very low levels of CBG) were similarly injected. In the colon and parotid, [3H]aldosterone binding was at least an order of magnitude higher than that of corticosterone; in the pituitary aldosterone binding was approximately three times that of corticosterone. We interpret these data as evidence that in the parotid and colon type I receptors are aldosterone selective by a non-CBG-requiring mechanism, whereas in the pituitary there appear to be both aldosterone-selective and nonselective type I sites.
Sheppard
K
K
Medical Research Centre, Prince Henry's Hospital, Melbourne, Victoria, Australia.
Funder
J W
JW
D000450:Aldosterone / Q000378:metabolism*; D000732:Androstanols / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D003106:Colon / Q000378:metabolism*; D003345:Corticosterone / Q000378:metabolism; D005260:Female; D007668:Kidney / Q000378:metabolism; D010306:Parotid Gland / Q000378:metabolism*; D010902:Pituitary Gland / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D018161:Receptors, Mineralocorticoid; D011987:Receptors, Steroid / Q000378:metabolism
D000732:Androstanols; D011965:Receptors, Glucocorticoid; D018161:Receptors, Mineralocorticoid; D011987:Receptors, Steroid; D000450:Aldosterone; C049154:11,17-dihydroxy-6-methyl-17-(1-propynyl)androsta-1,4,6-triene-3-one; D003345:Corticosterone