Citrulline does not relax isolated rat and rabbit vessels

1 The study was prompted by the report of Ruiz E. & Tejerina T., 1998 descr ibing endothelium-independent relaxation by L-citrulline via activation of particulate guanylate cyclase. 2 We compared the effects of L-citrulline and L-arginine in isolated aortic rings of rats and in isolated aortic, carotid and femoral artery rings of rabbits. 3 No significant relaxation to either L-citrulline or L-arginine was found in the concentration range of 10(-12) to 10(-3) M, while 3-morpholinosydnon imine hydrochloride (SIN-1, 10(-6) M) relaxed vascular tissues. 4 This study does not support the conclusion that L-citrulline has direct v asorelaxing action on vascular smooth muscle.