Effects of Hypophysectomy and Growth Hormone on Ploidy Distribution and Mitotic Activity of Rat Liver.

Abstract

Summary 1) Ploidy distribution patterns and mitotic activity in livers of young rats have been studied at various times following hypophysectomy, and compared with distributions in livers of rats of comparable weight. 2) It was found, within the time limits of this experiment, that there is a shift of ploidy distribution from one in which the diploid class of nuclei predominates to one in which the tetraploid class predominates. During this period of time the mitotic activity in these same livers decreases. 3) Hypophysectomy results in an arrest of the ploidy distribution consistent with the ratios present at the time of hypophysectomy. This is accompanied by a marked reduction in mitotic activity. 4) Growth hormone replacement in the operated animals restores both ploidy distribution pattern and mitotic activity to that seen in intact controls of comparable weight. The authors wish to acknowledge the technical assistance of Marilyn White and Marjorie Stoffel.