Effect of Pituitary Extracts on Basal Metabolic Rate.

Abstract

Previous studies on the effect of pituitary extracts on basal metabolic rate have not been conclusive, although an increase has been indicated. The work of Oliver Kamm who succeeded in separating the oxytocic and vasomotor principles of pituitrin, has made it possible to fractionate their effects on metabolism. In the present experiments the metabolic rates of male rats fasted approximately 24 hours, were determined in a Haldane-Pembrey apparatus, before and after the subcutaneous injections of chloretone-free pitocin, pitressin and pituitrin (surgical). The limit of error of the method was considered to be ± 5%.

A slight increase in metabolic rate was observed after the injection of pitocin. Doses ranging from 2.5 to 80 units per kilo showed an average rise in the oxygen consumption of 32% above the basal level, during the first hour after injection. Part of this rise, probably about 16%, was due merely to the effect of the injection. The average increase for the second and third hours after injection was 13%. The rise was not directly related to the size of the dose.

Results with small units of pitressin (17-40 units per kilo) were variable. Doses from 50-100 units per kilo decreased the oxygen consumption 22% in the first hour after injection. The average oxygen consumption for the second and third hours did not differ significantly from the basal.

Pituitrin (surgical) produced an average fall of 19% in the oxygen consumption in the first hour after injection and 7% in the 2 succeeding hours. A summary of results is shown in Table I.

We wish to thank Doctor Oliver Kamm, through whose courtesy Parke, Davis and Company has supplied us wiah pitocin and pit ressin.