Effect of Growth Hormone and Oxytocin Upon Milk Yield in the Lactating Rat.

Abstract

We have investigated the effect of growth hormone (GH) and oxytocin alone, and in combination, upon lactation in the rat. Amount of milk obtained by a litter of 6 during 30 minutes nursing on day 14 postpartum, expressed as percent litter body weight, was used as the index of response. Control yields averaged 3.8% with normal distribution. Removal of milk with aid of 0.1 USP unit/kg oxytocin intravenously resulted in 50% higher yield with more uniformity among individual values. GH injected subcutaneously from days 7-13 at dose of 1 mg/rat/day evoked a 41.1% increase in milk yield. Yields obtained in GH-treated lactating rats with aid of oxytocin were greater and mope uniform than with GH or oxytocin alone. GH had no effect upon pituitary, thyroid or adrenal weight/100 g body weight. GH caused a significant increase in percent weight gain of mothers but not their litters.