Hepatic or pulmonary ornithine decarboxylase and vitamin A status in Wistar rat, enzyme kinetics--influence of chloroform.

The ODC activity, initial enzyme in the polyamines synthesis, was studied in the liver and lungs of Wistar rat under avitaminosis A. In the liver: ODC activity is decreased by vitamin A deficiency but partially recovered with retinol repletion during 2 weeks. An intraperitoneal injection of chloroform markedly stimulates the ODC activity, as in the deficient rat as in the normal animal; the response following stimulation is even relatively higher under avitaminosis A. The Km value of ODC increases in the deficiency; intermediate values are obtained in retinol repletion. However the chloroform injection has no effect on the Km values under any of the nutritional state. In the lungs: The baseline ODC activity is slightly decreased in the deficient animals. The chloroform stimulation induced relatively a moderate increase in the normal rat (2 fold over baseline level); it is more intense (4 fold) in deficient animal and the ODC activity is well above those of normally fed control in absolute value. As in the liver, the enzyme Km increases in avitaminosis A and a retinol repletion partially attenuates this influence. Here again, the chloroform stimulation has no effect on the Km values.