Effect of pituitary hormones upon serum free fatty acid concentration of the rabbit.

Abstract

A previous study showed that the injection of a crude extract of hog pituitarjr glands in the rabbit causes a 10- to 15-fold increase in the serum free fatty acid (FFA) concentration within 2 hours. In the present investigation the effect of purified preparations of 9 pituitary hormones, including the recently described pituitary component “Fraction H” (which has previously been shown to be different from the recognized pituitary hormones), upon the rabbit’s serum FFA level was studied. The following hormone preparations were found to have no effect upon the serum FFA concentration: bovine GH (10 mg.), TSH (8.3 mg.), prolactin (10 mg.), FSH (10 mg.), and oxytocin (30 units). The following hormone preparations caused a modest increase in the rabbit’s serum FFA level 2 hours after the injection: porcine GH (Raben-Westermeyer preparation) (5 mg.), ICSH (10 mg.), and vasopressin (40 units). Purified ACTH and Fraction H were highly active in increasing the rabbit’s serum FFA concentration. After the injection of 0.25 mg. or more of purified ACTH or of Fraction H, serum FFA concentration increased from an average value of 250 μeq./L to 2000 to 3000 μeq./L. within I hour. Higher dosages of Fraction H caused a prolongation of the period of serum FFA elevation, and the appearance of lipemia 4 to 10 hours after the injection. The present study indicates that in the fed rabbit Fraction H and ACTH are the only identified components of the pituitary gland that are highly active in mobilizing FFA into the serum.