Studies on the salivary gland hormones labeled with I 131. 4. Studies on the degradation of I 131 labeled parotin by several tissue homogenates of rat.

Recently it was reported from this laboratory as one of a series of studies on the Salivary Gland Hormones, that liver and spleen were the main and characteristic sites of localization of radioactivity after administration of I 131 labeled Parotin to rats(Tanaka and Ito, 1958). And subsequently it was also observed that this characteristic localization of radioactivity in the liver and spleen and the rate of degradation of I 131-Parotin in vivo were remarkably decreased by the simultaneous injection of intact Parotin with the labeled Parotin to rats(Tanaka et al., 1958). This report presents the results of studies on the in vitro degradation of I 131labeled Parotin and other similarly radioiodinated proteins such as bovine serum albumin(B. S. A.), pituitary growth hormone(GH)and casein by several tissue homogenates of rat.