Citrulline does not relax isolated rat and rabbit vessels.

The study was prompted by the report of Ruiz E. & Tejerina T., 1998 describing endothelium-independent relaxation by L-citrulline via activation of particulate guanylate cyclase. 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. 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-morpholinosydnonimine hydrochloride (SIN-1, 10(-6) M) relaxed vascular tissues. This study does not support the conclusion that L-citrulline has direct vasorelaxing action on vascular smooth muscle.