<prompt> Endothelial derived relaxing factor is associated withRasC- mycBclnNOS  <response>: Ref Robbins 8p60;7e,72-73 ;9e p80 , it is firmly established this substance is nitric oxide NO.Endothelium produces NO which then diffuses to the vascular smooth muscle tissue, although these seems to be evidence that vasodilatory may also be of neuronal origin, rather than endothelial. NO is produced by the enzyme nitric oxide synthase and it relaxes smooth muscle tissue by promotig the synthesis of cGMP. 