Testosterone metabolites in dog bile

Testosterone-1,2-3H was injected intravenously into a male dog with a bile fistula and bile and urine collected. The radioactivity was excreted preponderantly in bile (52% of the injected dose) in 6 hours; only 12% appeared in the urine. Methods to study the biliary metabolites of testosterone in this and other animals were developed. Satisfactory conjugate patterns were obtained by fractionation on DEAE-Sephadex A-25 columns using two different elution systems. In addition to an unchanged fraction, six different monoglucuronide fractions were separated. No other conjugates were isolated. Lipidex 5000 column chromatography, TLC and paper chromatography were used for the isolation and purification of aglycone metabolites, which were further identified by co-crystallization methods. The biliary metabolites of testosterone were epiandrosterone (3beta-hydroxy-5alpha-androstan-17-one), etiocholanlone (3alpha-hydroxy-5beta-androstan-17-one), 5alpha-androstan-3beta, 17beta-diol, 5beta-androstan-3alpha, 17beta-diol and 5beta-androstan-3beta,17beta-diol.     

Molecular cloning of a tissue-specific protein kinase (C gamma) from human testis--representing a third isoform for the catalytic subunit of cAMP-dependent protein kinase

Two different mammalian genes for the catalytic subunit (C) of cAMP-dependent protein kinase have previously been characterized (C alpha, C beta). In the present study, we report the molecular cloning of a third isoform of C, from a human testis cDNA library, as well as the isolation of human cDNAs for C alpha and C beta. This third form of C, which we will designate C gamma, is clearly derived from a distinct gene and shows a tissue-specific expression. A close evolutionary relation between C gamma and C alpha was suggested by nucleotide homologies (86% inside the open reading frame, 81% in the 3'-untranslated region). Thus, the C gamma cDNA cross-hybridized with the 2.8 kilobase (kb) C alpha mRNA, present at high levels in most human tissues, as well as with a 1.8 kb C gamma-specific mRNA, which was only found at detectable levels in human testis. However, at the amino acid level, C alpha and C beta showed a close relationship (93% homology), whereas C gamma diverged significantly from both C alpha (83%) and C beta (79%). Taken together with the tissue-specific expression of C gamma, this suggests a pressure on C gamma during evolution, acting to modulate it in a functionally specific way. Certain amino acid substitutions make C gamma a distinct member of the cAMP-dependent subfamily of protein kinases, and suggest that C gamma may be distinct in its protein substrate specificity or its interaction with the different regulatory subunits.     

Induction of superoxide dismutase, chromosomal aberrations and sister-chromatid exchanges by paraquat in Chinese hamster fibroblasts

We have recently shown that Bloom syndrome fibroblasts have elevated levels of superoxide dismutase activity compared to those of normal fibroblasts. Based on this observation we decided to test whether an increased rate of superoxide radical production could be responsible for the induction of superoxide dismutase and of chromosomal aberrations and sister-chromatid exchanges characteristic of Bloom syndrome. Utilizing the superoxide-generating herbicide paraquat in Chinese hamster fibroblasts, we assayed the cells for dismutase activity, chromosomal aberrations and sister-chromatid exchanges. All 3 parameters investigated demonstrated a dose-dependent increase with paraquat and, consequently, with the superoxide produced. Since the induction of the enzyme is mediated by its substrate, the superoxide anion radical, we concluded that the increased dismutase activity (in Bloom syndrome and paraquat-treated cells) may be a secondary manifestation of an overall imbalance in oxygen metabolism and that this elevated enzymatic activity is insufficient to detoxify the high superoxide levels, which results in elevated levels of chromosomal damage.     

Autophagic degradation in rat liver after vinblastine treatment

Mechanisms of autophagic proteolysis in the liver have been studied using vinblastine. Vinblastine stimulated degradation by induced autophagy in a dose-related fashion [1, 2]. Insulin partially inhibits the increased rate of degradation and the formation of autophagosomes as well as the lysosomal fragility induced by vinblastine. Insulin has little effect, however, on basal, non-induced degradation rates. Vinblastine-induced autophagy enhances the degradation of both ‘old’ and ‘newly’ synthesized proteins and is therefore in that sense a random process. The administration of high doses of colchicine also augments proteolysis. This effect is attributed to increase in autophagy. The very nascent vinblastine-induced autophagosomes appear to lack hydrolytic enzymes and acquire them only after fusion with lysosomes. The autophagolysosomal population induced by vinblastine is heterogeneous with respect to shape, size, content and density. Isolated secondary lysosomes (‘residual bodies’) lacking morphologically recognizable sequestered membranes (degradable substrate) show no release of degradation products. Autophagosomes fuse with secretory vesicles originating from the Golgi apparatus.