CARDIOVASCULAR CHANGES DURING LACTATION IN THE RAT

Abstract

SUMMARY The effect of lactation on cardiac output, measured by Fegler's thermodilution technique, and on organ blood flow, measured by Sapirstein's indicator fractionation technique, has been investigated by studying three groups of rats: (1) on day 1 of lactation; (2) on day 12 of lactation, suckling a large litter; (3) on day 12, the young having been removed on day 1. Lactation was accompanied by a significant increase in the weight of the mammary glands, the liver and the small and large intestines and a decrease in the weight of the female reproductive tract and of the skin. Cardiac output in 12-day lactating animals was significantly higher than in non-lactating and in rats on day 1. The proportion of the cardiac output taken by the mammary glands, liver, gastrointestinal tract and their blood flow/g. tissue, increased. Skin blood flow increased, but not that of brain, heart or kidney.