Guinevere C. Smith

Respiratory Metabolism of Pigeons after Adrenalectomy and its Increase by Prolactin

Recent experience in the maintenance of adrenalectomized animals in fair or good condition without use of cortical hormones gives new interest and value to measurement of the basal metabolism of such animals, and the adrenal-pituitary relationship is now the subject of much investigation. The pigeon has been found useful in such studies. It seems to survive complete adrenalectomy readily, though it is best to do the operation in two stages and to inject desoxycorticosterone just before the second operation; thereafter pigeons maintain themselves well without special nutritional or hormonal supplements. Repeated metabolism measurements have been made on 12 such pigeons of various races (both sexes) and on 4 of these birds the ability of prolactin to increase the B.M.R. was demonstrated. Thirty measurements made at 30° C indicate that adrenal removal in pigeons has little effect on heat production; a decrease of 6% was found. Measured at 25 °C this decrease was also 6%. Respiratory quotients obtained after a 24-hour fast were the same in operated (0.73) and intact pigeons. In 10 tests made on birds from which a single adrenal was removed no significant effect was observed. The effect of adrenalectomy on the metabolism of the bird is thus found to be less though similar in direction to that previously reported by others for certain mammals. Interpretation of depressions noted in most mammalian tests is usually obscured by the regimen imposed to insure survival or by poor condition of the animals. In pigeons it seems probable that the observed small decrease in B.M.R. was the indirect result of some (presumptive) reduction in bodily activity and of some protection against low temperature. One thyroidectomized pigeon showed a 10% decrease in metabolism following adrenalectomy.

Effects of complete and incomplete hypophysectomy on basal metabolism of pigeons.

Summary Within 10-20 days after complete hypophysectomy the B.M.R. of the adult pigeon undergoes a pronounced decrease, but the extent of the indicated decrease is much influenced by the environmental temperature at which measurement is made. At the critical temperature (30°C.) the B.M.R. of 9 pigeons was decreased by 33% in 7 pigeons measured at 20°C. the decrease was only half as much, or 17%. Seven incompletely hypophysectomized birds (less than 4% of pituitary present) measured at 30° provide data which confirm the important rôle of temperature and further indicate that the B.M.R. of such birds is practically the same as that of the completely hypophysectomized pigeon. Pituitary fragments representing 10-25% of the total gland usually only partially sustain the normal rate of heat production. B.M.R. measurements made at 20° did not distinguish partial from complete hypophysec-tomies, and this provides a further indication that a truer measure of effect of hypophysectomy is obtained from tests made at the animals critical temperature.