Effect of experimental neurogenic hypertension on renal blood flow and glomerular filtration rates in intact denervated kidneys of unanesthetized rabbits with adrenal glands demedullated.

This study was undertaken to examine responses made by the renal circulation to increases in systemic blood pressure in unanesthetized animals. The kidneys were denervated and the adrenal glands demedullated to avoid such nervous or hormonal effects as might be reflexly induced by the procedure employed in neurogenically obtaining pressure increases via severing the depressor nerves and clamping the carotid arteries. Interest in this problem stems not only from the general importance of an understanding of basic pressure-flow relationships, but also from the attention directed to alterations in renal blood flow as an explanation of the possible role of the kidney in the genesis of hypertensive disease. It has been repeatedly shown that the most characteristic feature of the renal circulation is the constancy of renal blood flow which is maintained despite extensive variations in blood pressure. This was demonstrated in a classic experiment by Burton-Opitz and Lucas in 1911 (1). Renal blood flow was measured by stromuhr on the renal vein in dogs narcotized with chloroform or ether, and rises in arterial blood pressure were obtained by central excitation of the vagi. Characteristically no change in blood flow was detected despite pronounced rises in arterial blood pressure. This led them to conclude that the renal blood vessels tonically retain the normal size of the bloodbed. After renal denervation, in this preparation, the accommodation in increased pressure was lost and the renal blood flow was readily altered passively. However, Opitz and Smyth showed in dogs narcotized with morphine-pernactone that blood pressure variations elicited by the carotid sinus reflex did not alter renal blood flow as measured by stromuhr in intact or in denervated kidneys (2). The early literature dealing with the effect of changing pressure on renal blood flow as estimated by oncometer and stromuhr in anesthetized animals has been reviewed by Smith (3). An opportunity to measure renal blood flow and glomerular filtration rates in unanesthetized animals was provided with the introduction of clearance techniques. Bing, Thomas and Waples (4) induced chronic hypertension neurogenitally in dogs, and d .emonstrated th at the renal bl .ood flow and glomerular filtration rates remained constant or fell wi th the onset of increased blood pressures. The studies on the unanesthetized rabbit reported in this paper indicate