Solubilization and characterization of guinea‐pig pancreatic somatostatin receptors

Abstract

The solubilization of somatostatin receptors from guinea-pig pancreas by different non-denaturing detergents was investigated after stabilization of the receptors by prior binding of '"I-[Tyr' ']somatostatin or its analogue '251-[Leu8,~Trp22,Tyr25]somatostatin 28, to pancreatic plasma membranes.The somatostatin-receptor complexes were solubilized in a high yield by Zwittergent 3-14 (3-[tetradecyldimethylammoniol-1-propanesulfonate), a zwitterionic detergent. Other detergents, digitonin, Triton X-100, Chaps (3-[cholamidopropyldimethylammonio]-1 -propanesulfonate) and octyl P-D-glycopyranoside, achieved only partial solubilization. The recovery of receptor complexes was increased by glycerol.In order to characterize solubilized somatostatin-receptor complexes, membranes receptors were covalently labelled using N-5-azido-2-nitrobenzoyloxysuccinimide as cross-linking reagent before solubilization. Gel filtration chromatography analysis resulted in the identification of a major protein component of apparent MI = 93 000 which interacted with the two radioligands.In The solubilized somatostatin-receptor complex was adsorbed to wheat-germ agglutinin-agarose column and eluted by specific sugars.We concluded that the guinea-pig pancreatic somatostatin receptor in the membrane and in the non-denaturing detergent solution behaves as a protein monomer of apparent M I % 85000-90000. The somatostatin receptor is a glycoprotein which contains complex-type carbohydrate chains.Somatostatin, a tetradecapeptide (SI4) initially isolated from hypothalamus as an inhibitor of growth hormone secretion, has been found to exert inhibitory actions on various cellular processes in the central nervous system, gastrointestinal tract and pancreas [l]. High-affinity binding sites for somatostatin have been detected on plasma membranes or intact cells from various tissues including brain [2, 31, pituitaries [4, 51, adrenal cortex 16, 71 and endocrine pancreas [8]. We have recently demonstrated that pancreatic acinar cells possess specific somatostatin receptors [9, 101 which are involved in the inhibitory effect of the peptide on secretinstimulated cellular cyclic AMP [ll].

Ανιχνευση Υποδοχεων Σωματοστατινης Στον Αμφιβληστροειδη: Διαλυτοποιηση Και Βιοχημικος Χαρακτηρισμος Του Υποδοχεα

“…Στην υπόφυση οι Lewis and Williams (1987), Bruno and Berelowitz (1989) και Kimura et al (1989) Διαφορές στα μοριακά βάρη εμφανίστηκαν και στους υποδοχείς της σωματοστατίνης στο πάγκρεας. Η ανάλυση με αυτοραδιογραφία των φωτοσημασμένων, με διαφορετικά ιωδιωμένα σωματοστατινεργικά ανάλογα, υποδοχέων τους κατέταξε σε μια ευρεία περιοχή μοριακών μαζών από 21 έως 200 kD (Sakamoto et al, 1984;Susini et al, 1986;Srikant and Patel, 1986;Srikant and Patel, 1992-B;Zeggari et al, 1987;Cotroneo et al, 1988;Knuhtsen et al, 1988;Sakamoto et al, 1988;Knuhtsen et al, 1990;Marie et al, 1989;Thermos et al, 1990;Brown et al, 1990;Viguerie et al, 1988).…”