Weight and Composition of Organs During the Reproductive Cycle in the Rat

Abstract

Observations of 11 organ and gland weights in 40 parturient, 38 lactating, 26 resting and 79 unmated female rats were statistically analyzed for significant changes. One day after parturition there was an increase in absolute and relative weights of the liver and uterus and absolute weight of the ovaries compared with those of unmated littermate controls. Adrenal and thymus weights were decreased relative to body weight. After 3 weeks of lactation the pregnancy changes in liver, adrenal and thymus weights persisted. In addition, there was an increase in the relative and absolute weights of the heart, kidneys, and empty washed intestine. All organ and gland weights except that of the heart returned to the control levels 21 days after weaning a litter of seven or eight. These increases in weight of liver, kidneys and intestine were not accompanied by appreciable changes in moisture, fat or total nitrogen except for a significant increase in fat and decrease in nitrogen in the heart following lactation.