Comparative biochemistry of urea synthesis. 3. Activities of urea cycle enzymes in various higher and lower vertebrates

Abstract

4. The ratio of potassium to sodium decreased significantly with advancing age in kidney and heart tissue. 5. Nine tissues were analysed from a further five LK and five HK aged ewes. The skeletal muscle, liver, spleen and kidney (expressed on a fatand blood-free basis) of the aged HK ewes tended to have higher concentrations of potassium (1.5, 2*2, 3-6 and 1-9% respectively) and lower concentrations of sodium (10-7, 12 3, 9 2 and 4 8 % respectively) than those of the aged LK ewes. 6. Rumen epithelium from LK sheep had a significantly lower potassium concentration (19.5%) than that from HK animals. 7. The fat content of the skeletal muscle of aged LK sheep was significantly higher (17 g. of fat/kg. wet wt. or about 48 %) than that of aged HK'sheep but this difference was not found in a group of lambs of the same breed. We wish to express our appreciation to Dr A. T. Phillipson, Head of the Physiology Department, for his advice and very helpful discussions. We would also like to thank

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“…SCHIMKE [32] has shown that the enzymes of urea biosynthesis rise in a coordinate manner when increasing percentages of dietary proteins were fed to rats. BROWN et al [6] showed the simultaneous appearance of enzymes of the urea pathway during amphibian metamorphosis.…”

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“…Blood ammonia was determined as described by Gips and WilkensAlberts [8]. The methods of Brown and Cohen [3] were used for the quantitative assay of urea cycle enzymes. Amniotic cells were obtained by transabdominal amniocentesis after localization of the placenta by echoscopy in the 20th week of pregnancy, after one failure at 16 weeks.…”