The relationship between uracil nucleotide concentrations and glycogen synthesis in hepatocytes from fed and fasted rats.

The relationship between glycogen synthesis and uracil nucleotide content was studied in rat hepatocytes. When hepatocytes were incubated in the presence of uridine in the incubation medium there was an increase in the rate of incorporation of U-14C-glucose into glycogen. In hepatocytes incubated in the absence of uridine for 1 hr there were large decreases in the cellular contents of UDPG and UTP, while in the presence of 5 mM uridine the concentrations of these nucleotides increased 2 to 3 fold.

Effects of thyroid hormone on UTP content and uridine kinase activity of rat heart and skeletal muscle.

In rats made hyperthyroid by daily intramuscular injections of 250 microgram thyroxine (T4)/100 g body wt for 5 days, uridine kinase activity of extracts of psoas and cardiac muscle was markedly increased Vmax of the enzyme was elevated with no change in the apparent Km for uridine. In animals treated as above, significant increases in UTP and total uracil nucleotide contents were observed in heart and skeletal muscle. Twelve hours after a single intraperitoneal injection of 30 microgram/100 g body wt of 3,5,3'-triiodothyronine (T3), cardiac uridine kinase was significantly increased.

Effect of diabetes and fasting on the uridine triphosphate content and uridine kinase activity of rat cardiac and skeletal muscle.

The influence of diabetes and starvation on uracil nucleotide metabolism in muscle was studied. It was found that the uridine triphosphate (UTP) content of heart and diaphragm muscle was decreased in fasted and streptozotocin-diabetic rats and that insulin treatment of diabetic animals restored the UTP concentration to normal levels. The ATP content of heart tissue was not altered under these conditions.

Effect of uridine on cellular UTP and glycogen synthesis in skeletal muscle: stimulation of UTP formation by insulin.

The relation between cellular uracil nucleotides and ability to synthesize glycogen was studied in rat diaphragm incubated in vitro. In the absence of exogenous uridine the tissue content of UTP and rate of glycogen synthesis decreased with time. Uridine added to the medium increased cellular UTP and UDPG and stimulated glycogen synthesis.

Alteration by halothane of glucose and glycogen metabolism in rat skeletal muscle.

Exposure of resting rat diaphragm for one hour in vitro to halothane (1-1.5, 2-2.5 and 4-4.