Abstract
It has been observed that the injection of acid extract of cattle anterior pituitary produces in guinea pigs a condition comparable to that seen in Graves'disease in human beings. Loeb 1 has found a marked hypertrophy of the thyroid gland with diminution in the amount of colloid and a marked increase in the number of mitoses in the epithelial cells. Under the action of this substance the animals lose weight, and Siebert 2 has shown that there is an increase in their metabolic rate. Other effects corresponding to conditions found in Graves'disease have been established in subsequent investigations carried out in this laboratory. Inasmuch as tachycardia and nervous irritability are very prominent symptoms of Graves'disease in man it was of interest to study the effect of this extract of anterior pituitary on the heart rate and the reflex irritability of guinea pigs. Cursory observations of Loeb seemed to indicate that such an effect might possibly exist.
Twelve young male guinea pigs, approximately 200 gm. each, were chosen and normal records were obtained under a standard procedure using the electrocardiograph (lead one) to record the cardiac pulsations. Daily injections of 1 cc. of the acid extract were given to each of 6 guinea pigs, 3 of which had been thyroidectomized. The remaining 6 guinea pigs, 3 of which had been thyroidectomized, were used as controls, and were not injected. Records of the heart rate of all the animals were obtained on the 2nd, 4th, 9th, 11th, 16th, and 18th days. The heart rate of every animal in the group of injected non-thyroidectomized animals was faster on each occasion, after the second day of the injections, than that of any of the animals in the other groups.
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