A somatostatin receptor negatively coupled to adenylate cyclase in the human gastric cell line HGT-1

Abstract

Somatostatin receptors are demonstrated in the human derived gastric cell line HGT-1. Using 125I-Tyr 11-somatostatin as ligand, two classes of sites were characterized with apparent dissociation constants K D 1 = 0.9 × 10 −10 M and K D 2 = 4 × 10 −9 M and maximum binding capacities of N 1 = 20 and N 2 = 556 fmol per mg protein, respectively. These values are close to those previously reported in freshly isolated parietal cells (Reyl, F., Silve, C. and Lewin, M.J.M., Somatostatin receptors on isolated gastric cells. In S. Bonfils et al. (Eds.), Hormone Receptors in Digestion and Nutrition, Elsevier/North-Holland, Amsterdam 1979, pp. 391–400). Somatostatin binding to the high affinity sites was partially inhibited by the non-hydrolysable guanyl nucleotide analog Gpp(NH)p and by pretreating the cells with islet activating protein (IAP). Furthermore, IAP counteracted the inhibitory effect of somatostatin on histamine stimulation of adenylate cyclase. These findings are interpreted in terms of somatostatin interaction with the 41 000 Da adenylate cyclase GTP-dependent inhibitory subunit, Ni.