EVIDENCE FOR DECREASED STRUCTURALLY DETERMINED PREGLOMERULAR RESISTANCE IN THE YOUNG SPONTANEOUSLY HYPERTENSIVE RAT AFTER 4 WEEKS OF RENAL DENERVATION

Objectives To study the effects of denervation of the kidney on renal vascular resistance at maximal dilatation and renal function during th e development of hypertension in the spontaneously hypertensive rat (S HR), Methods SHR aged 6 weeks were subjected to left renal denervation or a sham-operation (n = 18 denervated, n=13 sham). When they were ag ed 10 weeks, pairs of denervated and sham-operated left kidneys were p erfused with 2% dextran in Tyrode's solution and pressure-flow and pre ssure-glomerular filtration rate (GFR) relationships at maximal vasodi latation were established. The awake mean arterial blood pressure, in- vivo renal function and renal noradrenaline content were also measured . Results There were no significant differences between the pressure-f low relationships for denervated and sham-operated kidneys. However, t here was a marked, parallel, shift leftwards in the pressure-GFR relat ionship (P < 0.001). Thus, the denervated kidneys commenced filtering at a lower threshold perfusion pressure than did the sham-operated one s. In-vivo renal plasma flow and GFR were significantly greater in the denervated left kidneys of SHR than they were in the contralateral ki dneys. The noradrenaline content in denervated kidneys was 5 +/- 3% of that in innervated kidneys, The awake mean arterial pressure was 135 +/- 1 and 138 +/- 2 mmHg in the denervated and sham-operated groups re spectively. Conclusion Denervation of the kidney of SHR aged 6 weeks o f age altered the pressure-GFR but not the pressure-flow relationship for these rats 4 weeks later, The results are compatible with there ha ving been an increase in average preglomerular and a decrease in post- glomerular vessel lumen diameters, These changes suggest that the rena l nerves affect the structural development of the renal vasculature in SHR.