STUDIES OF THE RELATIONSHIP OF THE THYROTROPIC, EXOPHTHALMIC AND FAT-MOBILIZING PRINCIPLES OF PITUITARY EXTRACT

Abstract

The effect of iodination with a dilute Lugol''s soln. on the thyrotropic, exophthalmic and fat-mobilizing principles of pituitary extract was studied. Thyrotropic activity was assayed by the chick thyroid wt method. Exophthalmos and fat mobilization were assayed in 200 g. guinea pigs following 2 daily sub-cut. injns. of prepns. of pituitary extract which originally contained 10 Junkmann-Schoeller units of thyrotropic activity. Intercorneal distances were measured with a simple instrument which is accurate to 0.1 mm., and fat-mobilization was detd. histologically by Scarlach R stains of frozen sections of the livers. Iodination at pH 5-6 resulted in irreversible inactiva-tion of the thyrotropic, exophthalmic and fat-mobilizing principles. Iodination at pH 4.2 produced up to 95% loss of thyrotropic activity, but sufficient exophthalmic and fat-mobilizing activity remained to produce effects. Suitable controls indicated that these effects could not be attributed to the thyrotropic principle alone. Treatment of the iodinated extract with thiouracil partly restored the thyrotropic activity and apparently slightly increased the exophthalmic and fat-mobilizing effects.