AbstractThe effects of porcine relaxin and insulin on blood glucose and on uterine and diaphragm glycogen were measured after 3 and 24 hr in alloxan-treated, hyperglycemic rats. Insulin caused a decrease in blood glucose and enhanced the glycogen concentration of diaphragm muscle but had no effect upon the uterus. Relaxin, which had no influence on blood glucose levels, increased uterine weight and uterine glycogen content; diaphragm glycogen concentration was depressed at 3 hr after relaxin administration. Neither insulin nor relaxin altered the action of the other hormone when given concurrently. Despite the structural similarities between insulin and relaxin, the two hormones exhibit distinctly different actions which were not found to overlap.