Effects of PTH and Ca2+ on renal adenyl cyclase

✍ Scribed by Nielsen, Susan T. ;Neuman, William F.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1978
• Tongue: English
• Weight: 442 KB
• Volume: 9
• Category: Article
• ISSN: 0091-7419
• DOI: 10.1002/jss.400090309

✦ Synopsis

The effects of calcium ion on the adenylate cyclase system was studied in isolated, renal basal-lateral plasma membranes of the rat. Bovine parathyroid hormone (bPTH) and a guanyl triphosphate analogue, Gpp(NH)p were used to stimulate cyclase activity.

Under conditions of maximal stimulation, calcium ions inhibited cyclic adenosine monophosphate (CAMP) formation, the formation rate falling exponentially with the calcium concentration. Fifty percent inhibition of either hPTH-or Gpp(NH)p-stimulated activity was given hy approximately 50 fiM Ca++. Also the Hill coefficient for the inhibition was close t o unity in both cases. The concentration of bPTH giving half-maximal stimulation of CAMP formation (1.8 X I O-'hl) was unchanged by the presence of calcium.

These data suggest that calcium acts at sonie point other than the initial hormone-receptor interaction. presumably decreasing the catalytic efficiency of the enzymic moiety of the membrane complex.