Biomedical subjects
Publications and source records attributed to U Lemm.
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Thermal inactivation studies performed with several membrane-bound enzymes such as chitin synthase, cytochrome c oxidase, nucleotidase, as well as bacterial, mitochondrial and plasma membrane ATPases from yeast in H2O and 2H2O indicated that most of these enzymes could not be protected by 2H2O against thermal inactivation. Only the Escherichia coli ATPase, which is located at the surface of the membrane, and the cytochrome c oxidase were stabilized by heavy water.
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The hydroxylation of 5alpha-dihydrotestosterone at C-2 in guinea pigs was measured with [1alpha,2alpha-T]5alpha-dihydrotestosterone as substrate by isolation of the liberated HTO ("Stoffwechsel-labile Markierung"). The hydroxylation measured in vivo by radiospirometry (condensation of body water with HTO from the expired air) was much higher in males than in females, due to the high hydroxylation capacity of the lung in males. In addition to lung, adrenal and liver showed a high, sexual organ low hydroxylation capacity for 5alpha-dihydrotestosterone.
The hydroxylation of testosterone and 5alpha-dihydrotestosterone at C-2 was measured quantitatively in vivo and in vitro in rats by using "metabolically labile" tritium labelled substrates. The enzyme activity was dependent on the sex and age of the animals. There was a good correlation between in vivo and in vitro experiments. Whereas testosterone was hydroxylated only in liver, 5alpha-dihydrotestosterone was hydroxylated in adrenals, kidney, lung and prostate as well. Hydroxylation was not sex-dependent in adrenals and lungs.
The hydroxylation at C-2 of testosterone and 5alpha-dihydrotestosterone is measured by isolation of HTO after incubating "metabolically labile" tritium labeled steroids with the enzymes. After hydroxylation of testosterone in rat liver 2alpha-hydroxytestosterone was isolated and identified by gaschromatography and mass spectra.
The in vivo C-2-hydroxylation of testosterone and 5-dihydrotestosterone in rats was measured by labilisation of tritium as HTO after injection of [1 alpha, 2 alpha-T]testosterone or [1 alpha, 2 alpha-T]5 alpha-dihydrotestosterone (radiospirometry). After experimental liver damage caused by CCl4 or after starvation for 60 h the hydroxylation of the androgens decreased. Similar results were gained by measuring the C-2-hydroxylation of testosterone, 5 alpha-dihydrotestosterone and estradiol.