BIOCHEMICAL PROPERTIES OF FRACTIONS OBTAINED FROM RAT ANTERIOR PITUITARY GLANDS BY DIFFERENTIAL CENTRIFUGATION1

Abstract

Anterior pituitary glands from normal and castrate adult female rats were homogenized in 0.88 [image] sucrose and separated by differential centrifugation into nuclear, large granule, small granule and supernatant fractions. The gonadotropic activity, the protein, pentosenucleic acid (PNA) and desoxypentose nucleic acid (DNA) contents, and the glycolytic, transaminase and succinoxidase activities of the homogenates and fractions of both kinds of glands were studied. The high level of gonadotropin found in the castrate as compared with the normal glands was concentrated in the small granule fraction, and it was removed from this fraction by extraction with isotonic saline. The distr. of protein in the 2 kinds of glands was studied. The granule fractions and the extract of the small granules of the castrate glands contained slightly less protein than the same fractions of normal glands. The DNA was recovered in the nuclear fraction and approx. 50% of the PNA in the supernatant fraction. Castration caused little change in the DNA and PNA. Glycolytic activity was essentially the same for the homogenates and fractions obtained from glands of normal and castrate rats, but gonadotropic hormone activity was much greater in the small granule fraction of glands from castrate as compared with normal animals. The major part of the transaminase was found in the supernatant fraction. The succinoxidase was distributed in the nuclear and granule fractions of both kinds of glands. These fractions as indicated by staining were found to contain mitochondria. On the basis of these results and those reported previously it appears that though gonadotropin is not associated to a significant degree with the mitochondria of the large granules nor with the submicroscopic particles recovered by high speed centrifugation of the supernatant fraction, it may be associated with those of the small granules.