Similarities between hamster pancreatic islet beta (HIT) cell vasopressin receptors and V1b receptors.

Vasopressin (VP) elicits almost identical insulin-stimulatory dose responses in isolated mouse islets and hamster beta (HIT) cells. We have further pharmacologically characterized HIT cell VP receptors by comparing the potencies of a series of VP agonists including the novel V1b agonist, desamino(D-3-(3'-pyridyl)-Ala2,Arg8)VP (d(D-3-Pal)VP), in stimulating insulin secretion and inositol phosphate (IP) production. The relative orders of potency of VP analogues were parallel in both respects: desamino-Arg-VP (dAVP) > Arg-vasotocin (AVT) = VP > oxytocin (OXY) > desamino-D-Arg-VP (dDAVP) > d(D-3-Pal)VP.

Vasopressin-stimulated insulin secretion and inositol phosphate production: interactions with glucose and phorbol esters.

Arginine vasopressin (VP) activates phospholipase C (PLC) and stimulates insulin secretion and inositol phosphate (insP) production in mouse islets and clonal hamster beta cells (HIT). The insulin response to VP is reportedly dependent on extracellular glucose and there is evidence that glucose also activates PLC. The interactions of VP and glucose have been further examined in HIT cells.

Somatostatin inhibits vasopressin-stimulated phosphoinositide hydrolysis and influx of extracellular calcium in clonal hamster beta (HIT) cells.

Vasopressin (VP) stimulates insulin secretion and inositol phosphate (InsP) production in clonal hamster beta cells (HIT) via a cyclic AMP-independent V1-receptor-mediated signal-transduction pathway. Somatostatin (SRIF) inhibited VP-stimulated insulin secretion, and the effects of SRIF were abolished by pretreatment with pertussis toxin. The Ca(2+)-channel blockers verapamil and nifedipine also inhibited VP-stimulated insulin secretion during 20 min incubations, but verapamil was ineffective at 2 min, and the effects of SRIF and nifedipine together were not addictive.