Cyclic AMP Production in Rat Calvariain Vitro: Interaction of Prostaglandins with Parathyroid Hormone

Abstract

The c[cyclic]AMP response of cultured rat calvaria to parathyroid hormone (PTH) and prostaglandins (PG) was studied in order to test whether PTH action is mediated by PG. PTH and PGE1 each caused an 8-fold increase in tissue cAMP during 15 min incubation. There was an additive response to the combination of the 2 agonists at maximally effective individual concentrations. Similar results were obtained when adenylate cyclase activity in bone homogenates was measured. Calvaria incubated for 60 min with PGE1 were desensitized to further stimulation by PGE1, but responded normally to PTH. Indomethacin, aspirin and phenylbutazone, 10-5 M, had no effect on cAMP response to PTH. At millimolar concentration these agents blocked the hormone response; response to exogenous PGE1 and fluoride-sensitive adenylate cyclase were inhibited. Apparently high concentrations of anti-inflammatory drugs on cAMP formation are nonspecific. Receptors in bone for PTH and PG probably are separate and independent, and cAMP response to PTH is not mediated by PG.