Dynamics of TGF-initiated nephron-nephron interactions in normotensive rats and SHR

Abstract

Proximal tubular pressure, glomerular filtration rate, and early distal tubule Cl- oscillate at 35 mHz in normotensive rats because of tubuloglomerular feedback (TGF); the oscillation bifurcates to chaos in spontaneously hypertensive rats (SHR). To examine the importance of TGF-initiated vascular interactions between nephrons in these dynamics, we measured tubular pressure simultaneously in two or more nephrons. The oscillations were synchronized in nephrons supplied by a common cortical radial artery. The correlation coefficient of pressure records from coupled nephrons was 0.86 +/- 0.02. Intratubular furosemide perfusion diminished the oscillation in both the perfused and the coupled nephron; total autospectral power in each of the nephrons and cross-spectral power were reduced to 45% of control. The correlation between noncoupled nephrons was not significant, and intratubular furosemide perfused in one nephron had no effect on adjacent but noncoupled nephrons. In SHR, the correlation coefficient of tubular pressure records was high from coupled nephrons only; furosemide diminished the autospectral power of pressure fluctuations to approximately 60-75% of control in both perfused and coupled nephrons, and cross-spectral power was affected by a similar amount. Nephron-nephron interactions, specific to vascular connectivity, persist in SHR and appear to be stronger than in normotensive rats.