Potassium depletion enhances renal compensatory hypertrophy in the nephrectomized rat

The purpose of the present investigation was to determine whether dietary K depletion would stimulate further renal growth in rats subject to 5/6 nephrectomy. In 36 rats renal mass was reduced by left 2/3 nephrectomy and right complete nephrectomy. Rats were fed either a normal or K-free diet. Two weeks later, total renal mass, water, protein and RNA content were measured. Twenty-nine rats served as the controls for the two surgical procedures, for treatment on the K-free diet or control diet, and for repeated cardiac blood sampling. Two weeks of dietary K depletion in the sham-operated rats caused a 13% increase in total renal mass compared to sham-operated controls. There was no difference in the weight of the removed right kidney or body weight before initiation of the diet in nephrectomized rats. However, after 2 weeks of consuming the K-free diet, there was a 48% increase in the weight of the remnant left kidney in the K-depleted rats compared to the nephrectomized control rats (K-depleted 2.31 +/- 0.147 g vs. control 1.56 +/- 0.059 g, p less than 0.001). Renal tissue water content was only slightly elevated (3%) in the K-depleted nephrectomized rats and could not account for the 48% increase in renal mass in these animals. In addition, RNA content mg/g dry weight was 75% higher in K-depleted nephrectomized rats compared to their nephrectomized controls. We conclude that K depletion causes a greater increase in renal mass and RNA content than would otherwise occur in response to nephrectomy in the rat.