Accretion and turnover of RNA in the renoprival kidney

Abstract

The relation of the synthesis and turnover of bulk renal RNA to compensatory growth of the mouse kidney was studied for 4 weeks after unilateral nephrectomy. During this time 75% of the original renal mass is ordinarily restored. The restoration predicted at equilibrium is 85% at 60 days. Dry weight, principally protein, is about 24% of the wet weight at all times. Estimations of bulk renal RNA and DNA by reliable methods show that the maximal increase inug RNA/ug DNA is 21% within 2 days in renoprival animals that eat well. Female mice and male mice that do not regain their original weight quickly have an increase of RNA/DNA of 15-20% on the 4th day. Elevated levels of RNA/DNA persist unchanged for almost 4 weeks. During a 75% restoration in renal mass, total RNA increases 36% and total DNA 14%, in contrast to virtually no change after sham operation. Catabolism of ribosomal RNA in both normal and renoprival kidneys proceeds by first-order kinetics with a half-life of 4.1 days. Most renoprival growth is hypertrophic and the average cellular accretion of bulk RNA is complete within a few days of nephrectomy, but hyperplasia is also important. The data also support the hypothesis that events soon after nephrectomy may be major stimuli to compensatory growth.