In vivo modulation of gap junctions and dye coupling between B-cells of the intact pancreatic islet.
The extent of gap junctions and dye coupling between insulin-producing B-cells was analyzed on islets of Langerhans isolated from adult rats treated for one day with glibenclamide, an insulin secretagogue, or diazoxide, a blocker of insulin release, or a combination of the two drugs. Glibenclamide treatment was associated with a marked depletion of the islet insulin content, an effect which was blocked by pretreatment of the rats with diazoxide. Diazoxide alone caused a marked increase in the plasma glucose level, and a decrease in the level of circulating insulin and in the hormone content of the B-cells. Quantitative analysis showed that (1) under control conditions, B-cells are connected by minute gap junctions (as evaluated on freeze-fracture replicas) and show a nonuniform and apparently restricted dye coupling (as determined by microinjection of the low-molecular-weight fluorescent probe Lucifer Yellow CH); (2) each of the three treatments tested significantly increased the relative and absolute gap junction area of the B-cells and the number of detectable, dye coupled B-cells per microinjection. After treatment with glibenclamide alone or with diazoxide plus glibenclamide, a 1.5-1.8-fold increase in gap junction area and a 2.7-3.7-fold increase in the number of dye-coupled B-cells were observed. In contrast, following treatment with diazoxide alone, gap junctions and dye coupling were found increased 1.8 and 8.7 times, respectively, as compared with control values.
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002450:Cell Communication / Q000187:drug effects; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D003981:Diazoxide / Q000494:pharmacology; D005614:Freeze Fracturing; D005905:Glyburide / Q000494:pharmacology; D007328:Insulin / Q000097:blood; D007365:Intercellular Junctions / Q000648:ultrastructure*; D007515:Islets of Langerhans / Q000648:ultrastructure*; D008297:Male; D051381:Rats
D001786:Blood Glucose; D007328:Insulin; D003981:Diazoxide; D005905:Glyburide