Renal vasodilation with acetylcholine but not secretin increases nonnutrient blood flow

To investigate the fact that, despite its renal vasodilator properties, acetylcholine (ACh) provides no protection against acute renal failure, we measured nutrient (NBF) and nonnutrient renal blood flow (NNBF) during ACh infusion. The effect of ACh and secretin on NBF in the outer and inner cortex and outer medulla using 133Xenon (133Xe) washout with freeze dissection analysis was determined. We then calculated NNBF as the difference between NBF in the entire cortex and outer medulla (133Xe washout) and total renal blood flow (TRBF) measured by electromagnetic flow probe. NNBF was also assessed from the 86Rubidium (86Rb) recovery after administration into the renal artery. ACh increased TRBF without increasing NBF, resulting in an increased calculated NNBF. ACh, but not secretin, increased NNBF in the kidney as measured with 86Rb. Thus we conclude that ACh selectively induces a large increase in NNBF in the kidney.