Single nephron comparison of the effect of loop of Henle flow on filtration rate and pressure in control and angiotensin II-infused rats.

Experiments were performed in control and angiotensin II-infused rats to test whether the tubuloglomerular feedback responses of early proximal flow rate (VEP) and stop flow pressure (PSF) are elicited by the same flow rate changes. Paired measurements in the same nephron revealed that VEP responses were shifted to the left compared to those of PSF. The flow rate at which the response was half maximum, V1/2, was 14.7 +/- 1.25 nl/min for VEP and 18.9 +/- 0.97 nl/min for PSF (p less than 0.05). This difference in flow dependency was abolished by angiotensin II infusion (V1/2 was 14.6 +/- 0.87 nl/min for VEP and 15.4 +/- 1.09 nl/min for PSF). Furthermore, angiotensin infusion markedly augmented the feedback response magnitude.