Julian R. Rachele

Further properties of isoglutamine-oxytocin; inhibition of pressor activity of vasopressin.

Summary 1) The isoglutamine isomer of oxytocin has been found to inhibit significantly the pressor activity of administered vasopressin in the anesthetized rat. 2) Various data suggest that acetic acid is lost when the polypeptide acetate is rigorously dried. Isoglutamine-oxytocin forms a crystalline flavianate salt.

Hydrogen isotope effects in the in vivo utilization of formate.

Abstract The hydrogen isotope effects in the utilization of formate in the rat were investigated with formate labeled intermolecularly with deuterium, tritium, and C 14 . Following the administration of this triply labeled formate, the isotope ratios of the formate excreted in the urine and of the methyl groups of tissue choline and creatine were determined and compared with the same ratios in the injected formate. The results indicate extensive selection among the hydrogen isotopes during the metabolism of formate. Intramolecular multiple labeling is suggested as a means of allowing less equivocal interpretations of isotope ratios in studies of the metabolism of C-H units.

The utilization in vivo of deuterio-C14 formate, labeled intramolecularly.

Abstract The utilization of formate labeled in the same molecule i.e., intramolecularly, with deuterium and C 14 was investigated in the rat. The deuterium and the C 14 contents of the urinary formate and of the methyl groups of choline and creatine, derived from formate, demonstrated the absence of the hydrogen isotope effects noted in earlier experiments performed with precursors labeled in separate molecules with the isotopes of carbon and hydrogen.

Effect of the presence of labile methyl groups in the diet on labile methyl neogenesis

Abstract The incorporation of deuterium from isotopically labelled body water into the methyl groups of body choline has been used as an indication of methyl synthesis in the rat in vivo. As a test of this concept the amount of isotope appearing in the body choline of rats on a methyl-free diet has been compared with that in rats receiving choline me methionine in the diet. The animals growing well without a source of methyl groups in the diet were found to incorporate approximately four times as much isotope into body choline as animals given choline or methionine.

Hydrogen isotope effects in the oxidation of labeled formate in vivo.

Abstract A hydrogen isotope effect has been demonstrated in the in vivo oxidation of formate to CO 2 . It has been suggested that this phenomenon may contribute in great part to the hydrogen isotope effects observed in a previous investigation on the in vivo utilization of formate (1).