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Type: Artigo de periódico
Title: Modulation Of Ca2+ And K+ Permeabilities By Oxotremorine-m (oxo-m) In Rodent Pancreatic B-cells.
Author: Bordin, S
Carneiro, E M
Boschero, A C
Abstract: The effects of the muscarinic agonist oxotremorine-m (Oxo-m) on 45Ca and 86Rb fluxes, insulin secretion, cytoplasmic Ca2+ concentration ([Ca2+]i) and membrane potential in pancreatic B-cells were studied. Oxo-m (40-200 microM) increased the [Ca2+]i by about 250 nM, irrespective of the glucose concentration present in the medium (2.8-22 mM). This effect was reduced by 50% upon the addition of EGTA. Oxo-m (50 microM) increased the 45Ca efflux from islets perifused in the absence or presence of [Ca2+]o, although under the former condition this efflux was transient. The difference between effluxes measured in the absence and presence of [Ca2+]o represents the sustained second component, which presumably reflects Ca2+ influx. In both the absence and presence of 11.2 mM glucose. Oxo-m (50 microM) transiently increased 86Rb efflux. In the presence of glucose, Oxo-m provoked a transient polarization of the B-cell membrane associated with an increase in the K+ permeability values. K+ permeability returned to basal values (no Oxo-m) after 1-2 min. These results indicate that the initial phase of Oxo-m-induced insulin secretion depends partially on intracellular Ca2+ release, and that the sustained enhancement of release depends on Ca2+ influx. The participation of a calcium release-activated current (ICRAC) is proposed to explain the sustained small changes in membrane potential.
Subject: Animals
Calcium Radioisotopes
Cell Membrane Permeability
Egtazic Acid
In Vitro Techniques
Islets Of Langerhans
Muscarinic Agonists
Rubidium Radioisotopes
Citation: Experimental Physiology. v. 82, n. 6, p. 967-76, 1997-Nov.
Rights: fechado
Date Issue: 1997
Appears in Collections:Unicamp - Artigos e Outros Documentos

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