Magnitude of TGF-initiated nephron-nephron interactions is increased in SHR

We compared the tubuloglomerular feedback (TGF)-initiated nephron-nephron interaction in spontaneously hypertensive rats (SHR) and normotensive Sprague-Dawley (SD) rats. Interaction strength was assessed by measuring stop-flow pressure (delta SFP) responses in pairs of nephrons, where only one nephron of the pair was microperfused. The vascular connection was determined from casts of the nephrons and vessels; length of arteriolar separation between the two glomeruli was measured on the casts. When microperfusion rate was increased from 5 to 50 nl/min, delta SFP in perfused nephrons was 10.6 +/- 0.6 and 10.2 +/- 0.7 mmHg [not significant (NS)] in SD and SHR, respectively. In the matched unperfused nephrons from the same cortical radial artery, delta SFP was 1.3 +/- 0.2 and 2.9 +/- 0.7 mmHg (P < 0.05) in SD and SHR. When the perfused and unperfused nephron originated from different cortical radial arteries, delta SFP in the unperfused nephrons was -0.1 +/- 0.2 and 0.0 +/- 0.3 mmHg (NS) in SD and SHR, respectively. In both strains, interaction strength varied inversely with glomerular separation. When the dependence on distance was taken into account, interaction strength was about threefold greater in SHR than in SD. We conclude that the nephron-nephron interaction is significantly greater in SHR. The dependence of interaction strength on distance separating the glomeruli suggests that the interaction is propagated along the preglomerular vasculature.