Cloned and Expressed Rat Ca2+-sensing Receptor

Abstract

We have stably expressed cDNA for the rat brain Ca[IMG]_16955_tex2html_wrap79.xbm">-sensing receptor in Chinese hamster ovary cells. Stimulation of phosphatidylinositol hydrolysis and arachidonic acid (AA) release displayed markedly cooperative responses to Ca[IMG]_16955_tex2html_wrap79.xbm"> with Hill coefficients of 4-5. Both phosphatidylinositol and AA responses were not detected below a threshold of 1.5 mM Ca[IMG]_16955_tex2html_wrap79.xbm">. Mg[IMG]_16955_tex2html_wrap79.xbm"> behaved as a partial agonist with only half the maximal inositol phosphate and AA responses displayed by Ca[IMG]_16955_tex2html_wrap79.xbm"> and with a more shallow concentration-response slope. The potency of Mg[IMG]_16955_tex2html_wrap79.xbm"> in augmenting inositol phosphate and AA responses, in the presence of 1.5 mM Ca[IMG]_16955_tex2html_wrap79.xbm">, implies that serum Mg[IMG]_16955_tex2html_wrap79.xbm"> concentrations attained in clinical conditions will influence the Ca[IMG]_16955_tex2html_wrap79.xbm">-sensing receptor.