EVIDENCE FOR ADENYLYL CYCLASE-DEPENDENT RECEPTORS FOR PARATHYROID-HORMONE (PTH)-RELATED PROTEIN IN RABBIT KIDNEY GLOMERULI

Studies were conducted to test whether parathyroid hormone-related pro tein (PTHrP) is able to stimulate adenylate cyclase activity in isolat ed rabbit glomeruli. Maximal stimulations were reached at 10(-7)M of h uman PTHrP-(1-34) or rat PTH(1-34) and showed a 3-3.3 fold increase ov er basal activity. The potency (EC50) values were close to 10(-9)M. Th e guanyl nucleotide GTP, at 10(-5)M, potentiated the effect of PTH and PTHrP but reduced their potency. The combined effect of maximal conce ntrations of PTHrP and PTH was not additive, and the PTH antagonist [N le8.18, Tyr34]-bPTH-(3-34)amide inhibited both PTHrP- and PTH-stimulat ed adenylate cyclase activities. These findings suggest that PTHrP cou ld affect glomerular function through changes in glomerular cAMP conte nt by interaction with PTH receptors.