Effects of parathyroid hormone on cyclic-AMP concentrations of in vitro Necturus maculosus gastric antrum

Abstract

The effects of bovine parathyroid hormone (bPTH 1–84) on the stimulation of intracellular cyclic-AMP [cAMP] were investigated in an in vitro preparation of Necturus maculosus antral mucosa. When the antrum was exposed to 1, 5, 10, or 100 n M bPTH 1–84, there was an ∼2-fold nonlinear increase in tissue [cAMP] over basal values. The pretreatment of the antral mucosa with 1 m M isobutylmethylxanthine (IBMX, a phosphodiesterase inhibitor) increased with detectability of mucosal [cAMP]. The addition of 1, 5, 10, or 100 n M bPTH 1–84 to tissues pretreated with IBMX resulted in an ∼3.5-fold linear increase in mucosal [cAMP] over basal values. The time course of the generation of mucosal cAMP to 10 n M bPTH 1–84 resulted in a small but significant transient increase at 2.5 min after the addition of bPTH 1–84 but no change in the medium [cAMP]. In tissues pretreated with 1 m M IBMX the response to 10 n M bPTH 1–84 was a large biphasic increase of [cAMP] at 2.5 min that progressively declined to near basal values by 15 min. There was also a significant sustained increase in the [cAMP] in the bathing medium at 2.5 min of tissues pretreated with IBMX followed by 10 n M bPTH 1–84. These results suggest the presence ofan adenylate cyclase that can be activated by a mammalian bPTH 1–84 in elevating intracellular cAMP levels in the N. maculosus antral mucosa.