Effects of dietary polyamines and clofibrate on metabolism of polyamines in the rat.

The activities of catalase, polyamine oxidase, diamine oxidase, ornithine decarboxylase, and peroxisomal beta-oxidation were assayed in homogenates from liver and small intestinal mucosa of rats which had been fed either a diet very low in polyamines or a diet containing five times the levels of dietary polyamines (putrescine, spermine, and spermidine) found in a standard rat diet. In rats fed the high polyamine diet, hepatic activities of catalase and polyamine oxidase were significantly decreased. Levels of the other activities were unchanged, except that intestinal ornithine decarboxylase was decreased. In rats treated simultaneously with clofibrate, the high polyamine diet restored activities of catalase, ornithine decarboxylase, and polyamine oxidase back to levels found in rats fed the low polyamine diet. The expected increase in activity of peroxisomal beta-oxidation was observed, although this was somewhat diminished in rats fed the high polyamine diet. Intestinal diamine oxidase activity was stimulated by clofibrate, particularly in rats fed the high polyamine diet. For the duration of the experiment (20 days), levels of putrescine, spermine, and spermidine in blood remained remarkably constant irrespective of treatment, suggesting that polyamine homeostasis is essentially independent of dietary supply of polyamines. It is suggested that intestinal absorption/metabolism of polyamines is of significance in this respect. Treatment with clofibrate appeared to alter polyamine homeostasis.

Enzymatic microanalysis of glycogen.

A specific and simple enzymatic method for the determination of glycogen in tissue, with a detection limit of about 1 microgram glycogen (6.2 nmol glucosyl residues) is described. Glycogen is converted to 6-phosphogluconate by means of amyloglucosidase, hexokinase, and glucose-6-phosphate dehydrogenase. The increase in NADPH is measured fluorometrically. Muscle tissue (5-20 mg) is hydrolysed in hot KOH (5.4 mol/l), neutralized and analysed. The glycogen-glucosyl content in wet rat diaphragm muscle is about 43 mmol/kg.