THE EFFECT OF VARIOUS ANTERIOR PITUITARY PREPARATIONS UPON BASAL METABOLISM IN PARTIALLY THYROIDECTOMIZED AND IN COMPLETELY THYROIDECTOMIZED GUINEA PIGS
In an investigation of the reasons for the different effects of various anterior pituitary preparations, 24 [male] guinea pigs, weighing between 350 and 500 gm., were used. Ten of these were as completely thyroidectomized as possible; 4 of these 10 were then given daily injections of 1 cc. of the acid extract of anterior pituitary substance, and 4 others were given 5 grain Armour anterior pituitary tablets by mouth daily; the remaining 2 of these 10 guinea pigs were used as completely thyroidectomized controls, to which no pituitary preparations were administered. Ten other guinea pigs were partially thyroidectomized, If to li lobes of the thyroid having been removed previous to the daily subcutaneous injection of 1 cc. of the acid anterior pituitary extract to 4 animals and the feeding of 5 grain Armour''s anterior pituitary pills to 4 others. The remaining 2 of these 10 were used as partially thyroidectomized controls to which no anterior pituitary preparations were administered. Four guinea pigs were used as normal control animals. The basal metabolism determinations were then made on each of the 24 animals every 4th day with the Haldane open circuit respiratory calorimeter. Each observation consisted of a 2-hr. period on this apparatus. The animals were starved for a period of 24 hrs. before the determinations were made. The injections and feedings of the anterior pituitary preparations were made previous to the starvation period. The experiments were continued for 28 days after the beginning of the administration of the anterior pituitary preparations. The results were: (1) for Armour anterior pituitary tablets, a marked rise in basal metabolism in partially and incompletely thyroidectomized as well as normal guinea pigs, being thus independent of thyroid changes; (2) for acid extract of cattle anterior pituitary glands a marked and rapid rise in basal metabolism in normal guinea pigs, in partially thyroidectomized guinea pigs, a slight but definite rise in basal metabolism, and in completely thyroidectomized guinea pigs, no change at all in basal metabolism, the effects being apparently entirely dependent on hypertrophic changes produced by the pituitary extract in the thyroid.