Comparative study on the effects of a hypoglycemic 2-substituted-2-imidazoline derivative (DG-5128) and tolbutamide on insulin secretion from and insulin synthesis in the isolated rat pancreatic islets.

2[2-(4,5-Dihydro-1H-imidazol-2-yl)-1-phenylethyl]pyridine dihydrochloride sesquihydrate (DG-5128) was found to stimulate the glucose-primed insulin secretion from the isolated rat pancreatic islets throughout the incubation period, unlike tolbutamide which stimulated it only in the initial phase of incubation. The effect of DG-5128 was more pronounced at a higher glucose concentration (5 mg/ml). In the islet perifusion study, DG-5128 was also found to stimulate the glucose-induced insulin secretion in both the first and the second phases of the reaction, in contrast to tolbutamide which stimulated only the first phase of insulin secretion from the perifused islets. DG-5128 gave no significant effect on the glucose-stimulated increase in incorporation of [3H]leucine into the proinsulin and insulin fractions, while tolbutamide significantly inhibited the incorporation especially at a low glucose concentration (1 mg/ml). These and the previous findings indicate that DG-5128 is a new class of hypoglycemic agent with a unique mode of action different from the known hypoglycemics ever reported.

Effect of pantethine on lipoprotein profiles and HDL subfractions in experimentally hypercholesterolemic rabbits.

A high-cholesterol diet caused in rabbits a great increase in beta-migrating VLDL and a significant decrease in HDL 2 (43% of normal) and HDL 3 masses (64% of normal), without significant changes in HDL cholesterol values. Chemical analysis of the HDL subfractions indicated an abnormal lipid-protein composition in the hypercholesterolemic rabbits, an increase in cholesterol and a decrease in the contents of triglycerides and phospholipid. When these rabbits were treated for about 1 month with pantethine, and intermediate precursor of coenzyme A, the increase in cholesterol levels was effectively prevented in the beta-VLDL (11%) and LDL fractions (43%) but, conversely, HDL-cholesterol was significantly increased (151%). In a separate experiment, HDL 2 and HDL 3 masses were calculated to be increased to 186% and 193%, respectively, by pantethine treatment, when compared with those in control cholesterol-fed rabbits. Serum apolipoprotein AI antigen levels were also significantly increased by the treatment.