Effect of cicletanine on the nitric oxide pathway in human umbilical vein endothelial cells

The purpose of this study was to evaluate the effects of cicletanine, a sli ghtly diuretic antihypertensive drug, on human vascular endothelial cells w ith regard to nitric oxide, intracellular calcium concentration ([Ca2+](i)) , cyclic nucleotide, inositol 1,4,5-trisphosphate (IP3), and prostacyclin g eneration. Primary cultured human umbilical vein endothelial cells were use d in this study. [Ca2+](i) was measured by fura-2/AM. Cyclic adenosine mono phosphate (AMP), cyclic guanosine monophosphate (GMP), IP3, and prostacycli n were measured by radioimmunoassay. Nitric oxide was measured by the Gries s method. Cicletanine had no effect on [Ca2+](i). Cicletanine (10(-6)-10(-4 ) M) increased cyclic GMP but decreased prostacyclin generation. Cicletanin e had no stimulating effect on cyclic AMP or IP3 generation. IP3 increased Ca-45 release from storage sites. Cicletanine decreased prostacyclin genera tion via increase in cyclic GMP. Cicletanine had no stimulating effect on n itrogen oxides for 2 h after incubation but increased it after 3-24 h, Pret reatment with L-N-G-monomethyl-arginine (L-NMMA) prevented this increase. T he inhibitory effect of L-NMMA was prevented by pretreatment with L-arginin e. These results indicate that nitric oxide and cyclic GMP may contribute t o the anti-hypertensive action of cicletanine.