Résumé
BACKGROUND: Recent studies have demonstrated that renin, alphasmooth muscle actin(ASMA) and aquaporin-1(AQP1) participate in the development of renal arterial system. The components of the renin- angiotensin system have been shown to function as growth factors, apart from their classical roles in controlling blood volume and homeostasis. Interestingly, the vasoconstrictor angiotensin II(ANG II) appears to participate in the regulation of angiogenesis in various tissues. The present study examined the effect of ANG II type-1(AT1) receptor blocker losartan given during pregnancy or newborn rats on the expression of renin, ASMA and AQP1 in the developing renal arterial system. METHODS: Pregnant and newborn rats received losartan(10 mg/kg/day) or saline for 4 and 8 days from E14 to parturition, and for 4 and 9 days starting at day 1 after birth, respectively. Kidneys of 17-day-old fetuses and 1-, 4-, and 9-day- old pups were processed for immunohistochemistry using antibodies to renin(1 : 10,000), ASMA(1 : 1,000), and AQP1(1 : 1,000). RESULTS: In all pregnant groups, there were no differences in immunostaining for renin, ASMA, and AQP1 between losartan treated groups and saline treated groups. In all newborn groups, however, blockade of AT1 receptor with losartan found to increase expression of renin and ASMA but to have no effect on expression of AQP1 in the developing renal arterial system. CONCLUSION: These results suggest that AQP1 expression is not associated with renin or ASMA expression during development of renal arterial system.