Abstract
There is a quantitative difference in the relative gonadotropic capacity of the pituitaries of various types of animals. The pituitaries of hogs and sheep contain much more of the gonad stimulating substances than do the pituitaries of beef. 1 According to Wallen-Lawrence and Van Dyke 2 similarly prepared extracts of beef and sheep glands showed the former to have less than one-tenth the activity of the latter.
During a series of studies of horse pituitaries collected at various times of the sexual cycle, and at different periods in pregnancy, we have compared their gonad stimulating activity with that of the pituitaries of other animals. The horse glands have considerably more gonadotropic activity than those of sheep, which have been the chief source of material for comparison.
The material was prepared by grinding the fresh glands, desiccating them in 2 volumes of acetone 3 times, completely drying in a warm current of air, and powdering.† A typical experiment is as follows: A total subcutaneous injection of 12.5 mg. of the dried powder administered twice daily over a period of 5 days to 21-22 day old rats produced ovaries weighing 97.4, 64.6, 35.0, 51.2, 35.4, 79.3, and 51.1 nig., average 59.1 mg.; 25 mg. total injection resulted in ovarian weight of 192, 107, 263.4, average 187.5 mg.; and 50 mg. produced ovaries 324.3, 369.2, 250.7, and 177.9 mg. respectively, averaging 280.5 mg.
Ovaries of rats injected with 50 mg. of dried sheep pituitary powder weighed 35-50 mg., while the ovaries of normal untreated controls weighed 12-14 mg. It is thus evident that the concentration of the sex stimulating hormones in horse pituitaries is approximately 4 times that of similarly prepared sheep material.
Furthermore, the effect of horse pituitary powder on the ovaries of immature rats appears to differ from that of sheep pituitary powder in that horse pituitaries seem to produce a greater follicular stimulation as compared to luteinization than those of similar preparations from sheep.
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