Abstract
Summary
The effect of variation in food intake and of unilateral nephrectomy on cellular proliferation in the kidney has been measured in weanling rats by means of autoradiography following flash labeling with tritiated thymidine. Labeling was used as an index of the proportion of cells engaged in DNA synthesis and thus in active proliferation. The labeling index decreased markedly from 0.65% to 0.06% after 24 hours of fasting. Refeeding after a 20-hour fast resulted in increased labeling after a 16-hour interval with return to normal levels at 24 hours. The stimulus of unilateral nephrectomy, which causes an increase in labeling index to 1.9% in animals fed ad libitum, failed to increase the index above 0.1% in fasting animals or in animals given 6 gm of food/day following a 4-day fast. The results suggest that renal work load may be the major factor stimulating cellular proliferation in the kidney, since loss of renal mass caused by nephrectomy failed to cause cellular proliferation in animals deprived of high levels of new metabolic products by fasting.
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