Tissue Distribution of Radioiodinated Human Growth Hormone in the Mouse 1

Abstract

Summary

The distribution of human growth hormone (HGH) labeled with ¹²⁵I was studied in mature and immature intact mice. The ¹²⁵I-HGH appeared to be biochemically homogeneous and possessed both biologic and immunologic activity. Uptake of ¹²⁵I-HGH in mice occurred initially in the liver, but the highest radioconcentration values occurred in the seminal vesicle (SV) of the male mice at 3.0 hr postinjection. Other tissues and organs in the male mice did not take up the radiolabeled HGH. Radio-uptake in a sexually equivalent organ of the female could not be demonstrated. ¹²⁵I-HGH levels were higher in the SV of immature than in mature male mice; however, this difference was not significant. The use of anti-HGH antiserum employed as a blocking agent specifically inhibited the uptake of ¹²⁵I-HGH in the SV of the mouse.

Growth hormone was discussed as a biologic synergist in an attempt to explain the localization of ¹²⁵I-HGH in the SV. Uptake of the radiohormone in the liver may have resulted from either (a) a blood clearing mechanism, or (b) stimulation of hepatic protein anabolism. It was suggested that continual stimulation of the sex accessory glands could result in hyperplasia and, conceivably, anaplasia.