INVOLVEMENT OF ECTO-ATPASE AS AN ATP RECEPTOR IN THE STIMULATORY EFFECT OF EXTRACELLULAR ATP ON NO RELEASE IN BOVINE AORTA ENDOTHELIAL-CELLS

The secretion of nitric oxide (NO) was stimulated by the addition of ATP or ADP, but not by AMP or adenosine, in cultured bovine aorta endothelial cells. Inhibitors of ecto-ATPase, NaN3 and Ap5A, significantly inhibited the stimulation, while an inhibitor of P-2Y-purinoceptor and ecto-ATPase, RB2, completely suppressed it. A non-hydrolyzable ATP analogue, AMP-PNP, stimulated NO release; the stimulation was completely suppressed by RB2 but not by NaN3 and Ap5A. Therefore, only P-2Y-purinoceptor was involved in the stimulation by AMP-PNP, while both ecto-ATPase and P-2Y-purinoceptor were involved in the stimulation by ATP and ADP. It is not clear whether the stimulation is dependent on the dephosphorylation activity of ecto-ATPase or not, but the enzyme appears to act as an ATP and ADP receptor for signal transduction through adenine nucleotides. (C) 1994 Academic Press, Inc.