PROXIMAL LUMINAL VOLUME AND FLUID REABSORPTION IN RAT KIDNEY

The relationship between proximal luminal volume and proximal salt and water reabsorption was studied in 21 non‐diuretic anesthetized male rats. Luminal diameters were measured in enlarged photographs of the surface of the capsulated kidney. Proximal reabsorption rates were estimated from Cin, which changed spontaneously in the range 0.4–1.6 ml/min g kidney weight (k.w.). Cin was further reduced in eight rats by compression of the renal artery. The mean proximal luminal diameter was 18.7 μ without compression of the renal artery and 19.6 μ during compression. There was no consistent relationship between estimated proximal reabsorption rate and proximal luminal diameter. It is concluded that proximal tubular volume was not the prime determinant of proximal salt and water reabsorption rate in rats under the conditions of these experiments. © 1968 Scandinavian Physiological Society