R. Qiu et al., CYCLIC-AMP IS NOT A DIRECT REGULATOR OF CALCIUM FLUX AND HYDROLYSIS OF PHOSPHOINOSITIDES IN HUMAN-LYMPHOCYTES, Immunopharmacology, 25(1), 1993, pp. 37-49
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.