EFFECT OF AMPHIPHILES ON NITRIC-OXIDE SYNTHASE IN ENDOTHELIAL-CELLS

Amphiphiles are known to modulate the activity of ATPase, phopholipase A(2), adenylate and guanylate cyclase amongst others and relax vascul ar smooth muscle. The effect of two amphiphiles, lysophosphatidylcholi ne (LPC) and digitonin on the activity of nitric oxide synthase (NOS), as measured by conversion of radiolabeled L-arginine to L-citrulline, has been studied. Neither digitonin (0.01 mmol/l) nor LPC (0.01 mmol/ l) influenced NOS activity in endothelial cell homogenates. Digitonin but not LPC stimulated NOS in intact endothelial cells. NOS activity w as markedly inhibited by Lr but not by D-omega-nitroarginine (D-NNA, 0 .1 mmol/l). L-NNA or D-NNA data demonstrate no effect of amphiphiles o n isolated NOS. NOS activation may occur as a result of detergent acti on on the membrane.