The Effects of L-Citrulline Pretreatment on the Isometric Tension of the Isolated Perfused Rat Aorta

The achievement of an effective compound for prevention/treatment of hypertension with fewer complications has been of interest in recent years. This study aimed to examine the effects of L-citrulline pretreatment on the tension of isolated rat aortic tissues precontracted by different vasoconstrictors. Sixteen male Wistar rats (300-350g) were randomly divided into two groups of control and test. The control group was injected 1ml distilled water, while the animal in the test group received 200 mg/Kg L-citrulline (CIT) i.p. for 7days. Rats were euthanized, their thoracic aortas were immediately separated and placed into a petridish containing cold Kerebs-Henseleit solution (KHS). The aorta were cleaned of the surrounding tissues and cut into 4 rings in the presence of 95% O2+5% CO2. The aortic rings divided into 6 subgroups, were suspended into organ bath containing KHS at 37oC. The isolated rings were contracted by 2×10-6 M phenylephrine (Phe) and 60Mm KCl. When the plateau was reached, a cumulative concentration of acetylcholine (Ach) was added into organ bath to induce relaxation. The effects of CIT on relaxation and the role of NO were tested using L-NAME as a pharmacological probe. The pretreatment of rats by CIT significantly (P<0.05) reduced the plateau contraction induced by Phe. CIT also significantly (P<0.01) decreased the contraction induced by KCl and L-NAME+Phe. However, cumulative addition of ACh significantly (P<0.001) decreased the vasoconstriction induced by Phe but not by KCl and L-NAME+Phe in both control and CIT-treated group. It suggests that, CIT can reduce the rat aorta vasoconstriction through releasing NO.