Functional somatostatin receptors on a rat pancreatic acinar cell line.
Somatostatin receptors from a rat pancreatic acinar cell line, AR4-2J, were characterized biochemically, structurally, and functionally. Binding of 125I-[Tyr11]somatostatin to AR4-2J cells was saturable, exhibiting a single class of high-affinity binding sites (Kd = 0.55 +/- 0.06 nM) with a maximal binding capacity of 258 +/- 20 fmol/10(6) cells. Somatostatin receptor structure was analyzed by covalently cross-linking 125I-[Tyr11]somatostatin to its plasma membrane receptors. Gel electrophoresis and autoradiography of cross-linked proteins revealed a peptide (Mr 80,000) containing the somatostatin receptor. Somatostatin inhibited vasoactive intestinal peptide (VIP)-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) formation in a dose-dependent manner. The concentration of somatostatin that caused half-maximal inhibition of cAMP formation (IC50 = 0.4 nM) was close to the receptor affinity for somatostatin. Pertussis toxin pretreatment of AR4-2J cells prevented somatostatin inhibition of VIP-stimulated cAMP formation as well as somatostatin binding. We conclude that AR4-2J cells exhibit functional somatostatin receptors that retain both specificity and affinity of the pancreatic acinar cell somatostatin receptors and act via the pertussis toxin-sensitive guanine nucleotide-binding protein Ni to inhibit adenylate cyclase.
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D008970:Molecular Weight; D010179:Pancreas / Q000378:metabolism*; D051381:Rats; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D017481:Receptors, Somatostatin; D013004:Somatostatin / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
D017981:Receptors, Neurotransmitter; D017481:Receptors, Somatostatin; D014660:Vasoactive Intestinal Peptide; D013004:Somatostatin; C012088:somatostatin, N-Tyr(1)-; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases