EARLY NARROWED AFFERENT ARTERIOLE IS A CONTRIBUTOR TO THE DEVELOPMENTOF HYPERTENSION

The kidney is probably critically involved in the development of essen tial hypertension, as in many genetic models of hypertension. We have investigated whether a narrowed renal afferent arteriole is involved i n the pathogenesis of hypertension in spontaneously hypertensive rats. Systolic blood pressure of 37 F-2 generation spontaneously hypertensi ve rats/Wistar-Kyoto rats was measured at age 7 weeks. The right kidne y was removed, and lumen diameter and media cross-sectional area of th e afferent arterioles were measured after having been fixed while rela xed and under a transmural pressure of 100 mm Hg. The uninephrectomize d rats continued until age 23 weeks, when mean blood pressure was meas ured. Mean blood pressure at 23 weeks was negatively correlated with l umen diameter at 7 weeks. Quartile analysis based on lumen diameter at 7 weeks showed that compared with rats in the top lumen diameter quar tile, rats in the bottom lumen diameter quartile had a reduced media c ross-sectional area at 7 weeks (17%), the same systolic blood pressure at 7 weeks, and an increased (16%) mean blood pressure at 23 weeks. W e conclude that in spontaneously hypertensive rats a narrowed lumen of distal afferent arterioles at 7 weeks contributes to later developmen t of increased blood pressure. This reduced lumen could be caused by i nhibited renal afferent arteriole growth.