Biochemical studies on the skin of fish, 4

Attempts were made to investigate the rate of incorporation of 14C-formate into G and Hx in the acid-soluble fractions of the skin of fishes (rainbow trout, Salmo gairdneri, and yamame, Oncorhynchus mason) and the influence of thyroxine treatment on their incorporation in vivo. 1. In comparing the rate of incorporation of 14C-formate into the acid-soluble purines in the liver, blood and skin, it was found that the incorporation occurred strikingly in the skin in the period from 2 to 24 hours. The incorporation of 14C-formate into the acid-soluble fraction increased in the skin during the 12 to 24 hour period, while it decreased remarkably in the liver and blood during the same period. 2. The ratio of the incorporation of 14C-formate into the sum of G+Hx to acid-soluble purines was approximately 60%. 3. The contents of G and Hx increased after the intraperitoneal injection of thyroxine (5μg/g B. W./10 days). Different effects, however, were observed with different diets. 4. The incorporation of 14C-formate into G and Hx in the skin of fish which were treated with thyroxine before 15 days was remarkably accelerated from 10 to 40 minutes after injection. At 40 minutes the specific activities of the G and Hx in the skin of fish with thyroxine were 10 times and 4 times higher respectively than that of controls.