CATION TRANSPORT BY PANCREATIC β‐CELLS: EFFECT OF 4‐AMINOPYRIDINE ON 86Rb+ AND 45Ca2+ FLUXES

• Published in: Quarterly Journal of Experimental Physiology 1987-10, Vol.72 (4), p.453-460
• Main Authors: Boschero, Antonio Carlos, Reis, Luis Carlos, Dias, Oneida, Delattre, Edson, Gonçalves, Antonio Ari
• Format: Article
• Language: English
• Subjects: 4-Aminopyridine; Aminopyridines - pharmacology; Animals; Biological and medical sciences; Calcium Radioisotopes; Cell Membrane Permeability - drug effects; Endocrine pancreas; Fundamental and applied biological sciences. Psychology; Glucose - metabolism; In Vitro Techniques; Insulin - metabolism; Insulin Secretion; Islets of Langerhans - drug effects; Islets of Langerhans - metabolism; Morphology. Functional localizations; Potassium - metabolism; Rats; Rats, Inbred Strains; Rubidium Radioisotopes; Vertebrates: endocrinology
• ISSN: 0144-8757; 1469-445X
• DOI: 10.1113/expphysiol.1987.sp003087

The effects of 4‐aminopyridine (4‐AP) on insulin release, glucose oxidation and 86Rb+ and 45Ca2+ fluxes of rat isolated islets were studied. 4‐AP (0·1 and 1·0 mM) did not alter the 86Rb+ fractional efflux. However, 10 mm 4‐AP significantly increased the 86Rb+ fractional efflux. 10 mM 4‐AP also reduced the insulin release from islets incubated over 90 min in the presence of both 6 and 16·7 mM glucose and from perifused islet in the presence of 16·7 mM glucose. 4‐AP (10 mM) only transiently increased the insulin release and the 45Ca2+ fractional efflux in the presence of 6 mM glucose. The 45Ca2+ fractional efflux was not changed when the islets were perifused at higher glucose concentration. At zero, 6 or 16·7 mM glucose, 4‐AP (10 mM) significantly increased the 45Ca2+ net uptake by islets incubated for 90 min. 10 mM 4‐AP significantly reduced the glucose oxidation of islets incubated for 120 min in the presence of 16·7 mM glucose. The effects of 10 mM 4‐AP on the dynamics of insulin release and 86Rb+ fractional efflux were poorly reversible. In conclusion, 4‐AP, at concentrations that did not alter the glucose metabolism, (0·1 and 1 mM), failed to affect the K+ permeability in β‐cells as judged by the measurements of 86Rb+ fractional efflux. At higher concentrations (10 mM) 4‐AP increased 86Rb+ efflux, decreased glucose metabolism and reduced insulin release.