A comparative analysis of the ontogenic development of rat liver sequential enzymes-tyrosine -ketoglutarate aminotransferase, p-hydroxyphenylpyruvate hydroxylase, and homogenitsate oxygenase

Cell cycle and 5'-Nucleotide phosphodiesterase activities in rat liver

The postnatal developments of liver and serum 5'-nucleotide phosphodiesterase (5'-NPD) in Fischer 344 rats were studied. The liver enzyme activities were found to correlate well with the growth of the liver as measured by the wet weight and percentages of liver cells in the G2/M phases of the cell cycle as determined by flow cytofluorometry. Therefore, this enzyme may be intimately related to the growth of the liver. Although the specific activities of the serum enzyme are three orders of magnitude less than that of the liver enzyme, very good correlation was obtained between the total serum and liver enzyme activities. This finding, therefore, suggest that the main origin of the serum enzyme is from liver. Multiple isozymes were detected in both liver and serum 5'-nucleotide phosphodiesterase after polyacrylamide gel electrophoresis.

Alterations in tyrosine aminotransferase isoenzymes of liver of rats as a function of age

The specific activities (units/mg protein) of tyrosine aminotransferase (TAT) and its isoenzymes, cytoplasmic (c-), mitochondrial (m-) and nuclear (n-TAT), of the liver of 6-, 35- and 76-week old male albino rats were determined. The activities of all the isoenzymes are highest at 6 weeks and are significantly lower at 35 weeks. Total TAT and c-TAT remain unchanged, m-TAT decreases and n-TAT increases significantly after 35 weeks. c-TAT was partially purified from the liver of rats of the three ages to study its kinetic and molecular properties. These properties apparently do not change as a function of age.