Comparative rates of synthesis of diphosphopyridine nucleotide by normal and tumour tissue from mouse mammary gland; studies with isolated nuclei

The activities of nicotinamide mononucleotide adenylyltransferase and of nicotinamide-adenine dinucleotide kinase in the livers of rats subjected to different hormonal treatments

1. The activities of NMN adenylyltransferase and of NAD(+) kinase have been measured in the livers of adrenalectomized or alloxan-diabetic rats and in the livers of rats treated with glucagon, pituitary growth hormone or thyroxine. 2. The activities of these enzymes have been compared with the effects of the same treatments on the nicotinamide nucleotide concentrations in the liver. 3. Alloxandiabetes (+37%) and thyroxine (+27%) both increased the activity of NMN adenylyltransferase. The other treatments were without effect on this enzyme. 4. Only thyroxine increased the activity of NAD(+) kinase significantly (+26%) although both adrenalectomy and glucagon tended to increase its activity. 5. The activity of NAD(+) glycohydrolase was measured in the livers of diabetic rats, and in the livers of rats treated with either growth hormone or thyroxine. Of these treatments, only growth hormone altered the enzyme activity (+26%, calculated on a total hepatic activity basis). 6. Female rats had a greater hepatic NAD(+)-kinase activity than males but there was no sex difference with respect to NMN adenylyltransferase. 7. The lack of correlation between the maximum potential activity of these three enzymes and the known changes of the nicotinamide nucleotides in each of the hormone conditions is discussed.

A procedure for the isolation of enzymically active rat-liver nuclei

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OXIDIZED PYRIDINE NUCLEOTIDES AND LACTIC ACID IN THE CORNEAL TISSUE OF RABBITS

The mean concentrations of oxidized pyridine nucleotides in the corneal epithelium and stroma of rabbits, determined fluorometrically in trichloroacetic acid extracts of scrapings from the frozen tissue, were 637 ± 130 and 58 ± 21 μg of DPN per gram of moist tissue respectively. The epithelial level was comparable to the reported content of some samples of rat liver and retina. The mean concentrations of lactic acid in corneal epithelium and stroma were 996 ± 158 and 771 ± 131 μg per gram of tissue respectively. Results suggested that in the cases of epithelial DPN and stromal lactate there is a slight advantage in using the paired eye as a control over an unmatched eye.