Adipokinetic Activity of Porcine Fraction H in the Rabbit—Guinea Pig—Rat and Mouse

Previous reports described the preparation from hog pituitary glands of a fraction (labeled “Fraction H”) which is highly active in mobilizing free fatty acids (FFA) into the serum of the rabbit. In this report, certain metabolic changes produced in the rabbit by porcine Fraction H are examined in more detail. The adipokinetic activity of porcine Fraction H in the rabbit, guinea pig, rat and mouse are compared. The injection of 3 mg of porcine Fraction H in the rabbit caused a 10-fold increase in serum FFA within 2 hours, which persisted for more than 8 hours. The adipose tissue of the rabbit treated with Fraction H exhibited hyperemia and contained an 11-fold greater average concentration of FFA than that of the normal rabbit. Lowering of serum CO2 content occurred during the mobilization of FFA. A slight reduction in R.Q. was found but there was no change in blood sugar concentration. Acetonemia did not appear. Four hours after the injection, there were 5- to 8-fold increases in the concentrations of liver and kidney triglyceride. Histologic examination revealed an accumulation of lipid in the cord cells of the liver and in the cells of the kidney tubules. Between 4 and 8 hours after the injection, a 7-fold increase in the serum triglyceride concentration developed. The addition of porcine Fraction H to rabbit perirenal adipose tissue in vitro caused a 5- to 7-fold increase in the rate of release of FFA from the adipose tissue into the medium. The injection of 2 mg of porcine Fraction H into the guinea pig caused a 3-fold increase in serum FFA concentration 2 hours after injection, and a 6-fold increase in liver triglyceride concentration 8 hours after injection. The serum triglyceride concentration was unchanged. Porcine Fraction H caused a 6- to 10-fold increase in the rate of release of FFA from slices of guinea pig adipose tissue in vitro. Porcine Fraction H at a dosage of 2 mg in the rat produced no increase in the concentrations of serum FFA or of liver triglyceride, and at a dosage of 0.5 to 3.0 mg in the mouse resulted in no increase in liver triglyceride concentration. The addition of porcine Fraction H to rat or mouse perirenal adipose tissue in vitro was unassociated with any change in the rate of release of FFA into the medium.