The renal L-arginine/nitric oxide pathway and erythrocyte L-arginine transport in spontaneously hypertensive rats

AIM: To investigate the changes of the renal L-arginine /nitric oxide pathway and the relationship of L-arginine transport between kidney and erythrocytes in spontaneously hypertensive rat (SHR). METHODS: Sixteen week old SHR, 16 week old SHR with captopril (CAP) treated for four weeks and 16 week old WKY rats were used in the experiment. L-arginine transport, NO synthase(NOS) activity, nitrite and cyclic GMP (cGMP) content were measured in renal tissue or erythrocytes. RESULTS: In the renal tissue, compared with that of WKY group, the Vmax of high-or low-affinity L-arginine transporter, NOS activity, NO₂^- and cGMP content of SHR group were significantly decreased (P＜0.01 or P＜0.05). The Vmax of high-affinity L-arginine transporter and NOS activity of CAP group were significantly enhanced as compared with SHR group (+90%, P＜0.01; +58.6%, P＜0.05). The NOS activity had significant positive correlation with the Vmax of high-affinity L-arginine transporter (r=0.585, P＜0.05). The changes of erythrocyte L-arginine transport were the same as that of kidney. The Vmax of SHR group was lower than that of WKY group (-30%, P＜0.01), and the Vmax of CAP group was higher than that of SHR group (+26.5%, P＜0.01). Km was not significantly changed. There is a positive correlation between the Vmax of L-arginine transport in erythrocyte and the Vmax of high- or low-affinity L-arginine transporter in renal tissue, (r=0.8434, P＜0.01, high-affinity; r=0.5255, P＜0.05, low-affinity). CONCLUSION: There existed a functional inhibition in L-arginine/nitric oxide pathway in the kidney of SHR. It can be recovered obviously by captopril treatment. The changes of L-arginine transport in kidney coincide with that in erythrocyte.