Abstract
Collip and coworkers have recently reported metabolic stimulation in rabbits, guinea pigs, and rats occurring within a few hours following injection of certain pituitary extracts. 1 , 2 , 3 The substance in the extracts producing this stimulation was called the “specific metabolic principle” of the pituitary. From the similarity in chemistry and occurrence in extracts, as well as from certain differences between these and other known pituitary hormones, it was suggested that the specific metabolic principle and the melanophore hormone might be identical. In view of the previous report of Zondek and Krohn 4 that “Intermedin” did not affect the metabolism of rabbits, it seemed worth while to study the subject further.
Accordingly, the effect on oxygen consumption of various melanophore hormone preparations was studied in rats. A modified Benedict spirometer was used to measure oxygen consumption. The rats were kept at room temperature but the metabolism was measured at 28°C. Comparable results were obtained with normal, thyroidectomized and hypophysectomized rats, and with rats recently fed as well as rats fasted 12-18 hours.
The usual procedure was to measure the basal rate in the morning, inject the extract after 2-3 hours, and measure the oxygen consumption over the following period of 8 hours without removing the rat from the machine. Using this technic, basal oxygen consumption for normal rats averaged 211 l/sq.m./day, for thyroidectomized rats 160, and for hypophysectomized rats 137. Control studies are shown in Fig. 1. On the ordinate is the percentage change in oxygen consumption over the basal value. Each column represents the highest reading obtained after injection in one experiment. Fig. 2 summarizes only the positive findings with various pituitary extracts.
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