Studies on metabolism of vitamin A. The effect of the stage of vitamin A deficiency on sulphate activation in rat liver

1. The synthesis of ;active sulphate' in rat liver was studied at various stages of vitamin A deficiency, with the corresponding pair-fed controls. 2. The activity was significantly decreased even at the onset of the deficiency, and at the acute stage there was further loss. 3. Only at the earlier stages of the deficiency was the addition of retinol, in vitro, fully effective in restoring the lost activity; retinoic acid was partially active. No such restoration was possible at the acute deficiency stage.     

Role of vitamin A in sulphate metabolism: Studies on the enzymic activation of sulphate by various tissue extracts of normal and vitamin A-deficient rats

1. The enzymic activation of sulphate by various tissue extracts of vitamin A-deficient rats and their pair-fed controls was studied. 2. Vitamin A deficiency does not impair the enzymic activity in liver, colon and brain. However, a significant decrease in activity was observed in epiphyseal cartilage.     

Early effect of myo-inositol deficiency on phosphatidylinositol metabolism in rat liver

Young rats (100 g) were fed either a myo-inositol-deficient or supplemented (control) diet for up to 14 days following a 12 h fast. At various times during this period animals were killed, livers were removed, and a microsomal fraction was prepared and assayed for CDPdiacylglycerol inositol transferase activity and for phosphatidylinositol-inositol exchange activity. Within 2 days after beginning the regimen, rats consuming the deficient diet had a 40% lower activity of the transferase than rats consuming the control diet. This difference was maintained throughout the feeding period and developed simultaneously with the accumulation of triacylglycerol in the deficient livers. In contrast, the specific activity of the exchange enzyme was unchanged by feeding the deficient diet.     

The effect of streptozotocin-induced diabetes on glycogen metabolism in rat kidney and its relationship to the liver system.

The effects in kidney of streptozotocin-induced diabetes and of insulin supplementation to diabetic animals on glycogen-metabolizing enzymes were determined. Kidney glycogen levels were approximately 30-fold higher in diabetic animals than in control or insulintreated diabetic animals. The activities of glycogenolytic enzymes i.e., phosphorylase (both a and b), phosphorylase kinase, and protein kinase were not significantly altered in the diabetic animals. Glycogen synthase (I form) activity decreased in the diabetic animals whereas total glycogen synthase (I + D) activity significantly increased in these animals. The activities were restored to control values after insulin therapy. Diabetic animals also showed a 3-fold increase in glucose 6-phosphate levels. These data suggest that higher accumulation of glycogen in kidneys of diabetic animals is due to increased amounts of total glycogen synthase and its activator glucose 6-phosphate.