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-cells"
1 Krannert Institute of Cardiology, Indiana School of Medicine, Indianapolis, IN, 46038, USA
2 Department of Pediatrics, Section of Hematology/Oncology, University of Chicago, Chicago, IL, 60637, USA
3 UNISSER, Departmento de Medicina Experimental, Facultad de Medicina, Hospital General de Mexico, Universidad Nacional Autonoma de Mexico, Mexico, D.F, 06726, Mexico
* To whom correspondence should be addressed. E-mail: eperez{at}servidor.unam.mx.
Connexin36 (Cx36) is the only gap junction protein that has been unambiguously demonstrated to be expressed in rodent pancreatic 
-cells at the present time. However, properties of gap junction channel unitary currents between -cells remain unrevealed. The aim of this study is to investigate whether Cx36 forms functional channels in -cells. To address this issue, we extended the characterization of macro- and micro-scopic biophysical properties of junctional currents under dual whole-cell voltage clamp isolated pairs of freshly dispersed mouse -cells. A high incidence of electrical coupling (80% n=20) was recorded between cell pairs with a mean junctional conductance (gj) of 355 ± 45 pS. Transjunctional voltage dependence of junctional channels was found in three out of seven cell pairs with high input membrane resistances. Steady-state junctional conductance and transjunctional-voltage relation was well described by a two-state Boltzmann equation with the following parameters: Gmax=1.0, Gmin= 0.3 and 0.28, A= 0.21 and 0.23, and Vo=-85 and 87 mV for negative and positive potentials respectively. Halothane reversibly uncoupled -cell pairs and, during recovery, unitary conductances (
j) of 5-10 pS were recorded while using patch pipettes containing mainly CsCl. These properties are similar to the ones previously described by others for connexin 36 (Cx36) channels expressed in mammalian cell systems. In contrast, we found that -cell junctional currents were not sensitive to quinine. The expression of Cx36 transcript and protein in islets and freshly dispersed cell preparations was confirmed by RT-PCR and immunofluorescence studies. In conclusion, biophysical properties of junctional channels between -cells are similar but not identical to those previously described for homomeric Cx36 channels. Cell mechanisms that may account for these differences are discussed.
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