Characterization of 17-β-Estradiol-dependent and -independent Somatostatin Receptor Subtypes in Rat Anterior Pituitary

摘要: Abstract Previous studies from this laboratory showed that treatment with 17-beta-estradiol (E2) caused an acquisition of inhibitory effect somatostatin (SRIF) on prolactin release increased number SRIF-binding sites in the rat anterior pituitary. The aim study was to characterize E2-dependent SRIF receptor comparison E2-independent one, which expressed ovariectomized rats. following observations were obtained: 1) both and receptors, measured 125I-Tyr11-SRIF as a radiolabeled ligand, enriched plasma membrane fraction cells, displaying single class binding site (E2-dependent: Kd, 32 pM, Bmax, 2.3 pmol/mg protein; E2-independent: 83 0.26 protein). ligand receptors sensitive monovalent divalent cations, GTP. 2) Among analogs tested, relative potencies SRIF28 its analog cyclosomatostatin compared lower than one. 3) A cross-linking N-hydroxysuccinimidyl-4-azido-benzoate revealed molecular weight cross-linked approximately 94,000, whereas one 82,000, irrespective presence reducing reagent. normal male or female pituitary similar type. 4) Both types solubilized by sucrose monolaurate, adsorbed wheat germ agglutinin-agarose column, eluted N-acetyl-glucosamine. 5) inhibited forskolin-stimulated adenylate cyclase activity membranes E2-treated rats, but it did not E2-depleted membranes. These results demonstrate there are at least two subtypes pituitary, is exclusively E2, these distinct respect specificity, weight, coupling inhibition.