Effect of gastrointestinal hormones on isolated bovine parathyroid cells

The effects of gastrointestinal hormones on cAMP accumulation and parathyroid hormone (PTH) release were investigated in dispersed bovine parathyroid cells. Secretin (10 (-7) M) caused a 4- to 6-fold increase in cAMP accumulation, while glucagon, vasoactive intestinal peptide, and gastrin caused little if any stimulation. Cholecystokinin caused a 2- to 3-fold increase in cAMP accumulation at 10(-6) M, but this effect may be related to contamination with endogenous secretin since synthetic cholecystokinin octapeptide had no effect. Maximal intracellular cAMP accumulation due to 10(-7) M secretin was reached within 5 min and returned to control over the next 30-60 min, concomitant with a progressive rise in extracellular cyclic nucleotide. cAMP accumulation was half-maximally stimulated by 5 x 10(-9) to 1 x 10(-8) M secretin and was unaffected by alpha- or beta-adrenergic or dopaminergic blockers. Parallel effects were noted on PTH release : 10(-8) M secretin caused a 20-50% increment in PTH release at 15 min which persisted for up to 2 h; PTH release was stimulated half-maximally by approximately 6--8 x 10(-9) m secretin. The specificity of the observed results for secretin and the lack of effect of adrenergic antagonists suggest the presence of a receptor for secretin on dispersed bovine parathyroid cells. These results also suggest the possibility that secretin may modulate parathyroid function in vivo in the cow.