FACTORS WHICH DETERMINE RENAL WEIGHT

Abstract

The kidney weights of 2 groups of albino rats, killed when 220 days of age, were not affected by pregnancies which had terminated for one group at approximately 8 days previously and for the other at about 45 days before. The kidneys of the pregnant animals were slightly increased in weight but this enlargement was of the same degree as the increase in the size of the organism as a whole. On the other hand, the heart increased in weight 5.1% and the liver 19.5%, both in relation to the body surface, in the group examined 8 days after pregnancy. When 45 days were allowed to elapse this increase in weight had disappeared. Age has no effect upon the capacity of the kidney to keep pace with the enlargement of the whole organism which results from pregnancy, for a pregnancy terminating just before death in rats which were killed when 400 days old had produced no effect upon the weight of the kidneys in relation to body size. Almost identical with the changes found in the younger rats were the increases in the heart weight of 6.0% and the liver weight of 20% over that of the body as a whole. A 45-day period of lactation ending just before death in albino rats killed when 220 days of age caused an increase in the weight of their kidneys of 8.2% more than the increase in the size of the organism as a whole. The high food intake of the lactating group suggested that this renal hypertrophy was the result of a high protein intake rather than due to the lactation itself. The increase in liver weight in relation to body surface of 19.5% found just after pregnancy, but which had disappeared 45 days later, was retained (22.4%) when the animals were allowed to lactate. The increase in the weight of the heart in proportion to body size of 5.1 %, due solely to pregnancy, was not only retained but further increased to 10.9% by the period of lactation.