CYCLIC-AMP IS NOT A DIRECT REGULATOR OF CALCIUM FLUX AND HYDROLYSIS OF PHOSPHOINOSITIDES IN HUMAN-LYMPHOCYTES

The regulatory effects of adenosine 3',5'-cyclic monophosphate (cAMP) on Ca2+ flux and phosphatidylinositol (PI) turnover in human lymphocyt es were studied. cAMP did not affect the intracellular accumulation of Ca2+ induced by phytohemagglutinin (PHA) and histamine-trifluoromethy l toluidide derivative (HTMT) in peripheral blood lymphocytes (PBL). I n addition, cAMP also did not alter Ca2+ flux induced by PHA, anti-CD3 , or PAF in T cells, or by anti-IgM and HTMT in non-rosetted cells. Si milarly, cAMP did not inhibit IP accumulation induced by HTMT in PBL, anti-CD3 in T cells, and by anti-IgM or HTMT in non-rosetted cells. Th e only exception was the synthesis of IP induced by PHA in T cells tha t was inhibited by cAMP. Furthermore, prolonged treatment of T cells w ith cholera toxin inhibited Ca2+ accumulation in response to CD3. The degree of inhibition of Ca2+ and IP responses was not proportional to the levels of intracellular cAMP generated.