title: Characterization of steroid receptors in the gut and kidney of the frog (Rana catesbeiana) and in the gut of the turtle (Chrysemys picta).
abstract: Paraglucocorticoid- and paramineralocorticoid-binding cytosolic receptors (pGR, pMR) were demonstrated in the intestine and kidney of the frog, Rana catesbeiana and in the intestine of the turtle, Chrysemys picta, in the presence of sodium molybdate. These receptors were of high affinity and low capacity with the following binding parameters: pGR:Kd:frog intestine (FI), triamcinolone acetonide (TA): 3.3 nM, corticosterone (B): 3.4 nM; frog kidney (FK), TA:4.3 nM, B: 9.3 nM; turtle intestine (TI), TA: 4.8 nM; Nmax: FI, TA: 357, B: 371; FK, TA: 301, B: 157; TI, TA: 350 fmol/mg protein. pMR:Kd: FI, aldosterone: 0.9 and 90 nM (biphasic curves); FK, aldosterone: 0.6 and 36 nM (biphasic curves); Nmax: FI, 13 and 147 fmol/mg protein; FK, 78 and 109 fmol/mg protein. The receptor had the following ligand affinities: pGR: FI and FK: triamcinolone acetonide greater than DOC greater than 11 beta-hydroxyprogesterone greater than progesterone greater than corticosterone greater than cortisol greater than aldosterone greater than 11-dehydrocorticosterone greater than 17 alpha-hydroxyprogesterone greater than cortisone; TI: triamcinolone acetonide greater than corticosterone greater than progesterone greater than DOC greater than cortisol greater than aldosterone; pMR: FI and FK: corticosterone greater than 11 beta-hydroxyprogesterone greater than aldosterone greater than triamcinoline acetonide = cortisol greater than DOC greater than 11-dehydrocorticosterone greater than progesterone greater than 17 alpha-hydroxyprogesterone greater than cortisone. Androgens, estrogens or 18-hydroxycorticosterone did not compete for binding in either tissue. The heat activated frog receptors did not bind to naked DNA, though the turtle receptor did. It was possible to show that cytosol receptor-ligand complexes from all tissues were bound by nuclear acceptor sites. On linear sucrose gradients, the FI TA-receptor complex sediments with a single peak (7.5S), the FK TA-receptor complex gave two peaks (8.0 and 4.4S) and the TI TA-receptor complex showed a single peak (9.0S). The hydrodynamic parameters of the pGR's were determined by gel exclusion on Sephacel S-300. The following results were obtained: Mr: FI, 265, 80, 40 kDa (multiple proteins); FK, 280, 60, 20 kDa (multiple proteins); TI, 366 kDa; Rs: FI, 6.9, 3.9 nm; FK, 6.9, 2.9 nm; TI, 7.6 nm; f/f0: FI, 1.6; FK, 1.6; TI, 1.6. It is suggested on the basis of the binding and hydrodynamic parameters that non-mammalian epithelia corticosterone receptors have undergone biochemical evolution from one class of vertebrates to another.
mesh_terms: D000450:Aldosterone / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D002467:Cell Nucleus / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D003345:Corticosterone / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D005260:Female; D007413:Intestinal Mucosa / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D011892:Rana catesbeiana / Q000378:metabolism*; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D018161:Receptors, Mineralocorticoid; D011987:Receptors, Steroid / Q000378:metabolism*; D014222:Triamcinolone Acetonide / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism; D014426:Turtles / Q000378:metabolism*
chemical_list: D011965:Receptors, Glucocorticoid; D018161:Receptors, Mineralocorticoid; D011987:Receptors, Steroid; D000450:Aldosterone; D004247:DNA; D014357:Trypsin; D014222:Triamcinolone Acetonide; D003345:Corticosterone