ISSN:
1432-2013
Keywords:
Key words Mesangial cell
;
Cell swelling
;
Ion currents
;
Intracellular Ca2+ activity
;
Cl
;
conductance
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Membrane voltage (V m) and ion currents of rat mesangial cells in primary culture were measured with the patch-clamp technique in the fast whole-cell configuration. V m was −44 ± 1 mV (n = 138). A reduction of the osmolality from 290 to 190 mosmol/kg depolarized V m from −44 ± 1 to −29 ± 1 mV (n = 118) and increased the inward and outward conductances (G m) from 14 ± 2 to 39 ± 4 nS and 13 ± 2 to 37 ± 4 nS (n = 84), respectively. During the hypotonicity-induced depolarization the cell capacitance increased significantly from 33 ± 3 to 42 ± 4 pF (n = 40). The effect of hypotonic cell swelling on V m was increased in a bath with a reduced extracellular Cl− of 32 mmol/l (by 71 ± 4%, n = 23), indicating that a Cl− conductance was activated. The permselectivity of this conductance was I−≥ Br− 〉 Cl−. The V m response was not affected in the presence of a reduced extracellular Na+ of 5 mmol/l (n = 13) and was inhibited in a solution with reduced extracellular Ca2+ concentration (by 63 ± 9%, n = 14). In microfluorescence measurements with the Ca2+-sensitive dye fura-2 hypotonic cell swelling induced a sustained increase of the intracellular Ca2+ activity, [Ca2+]i (n = 19). The increase of [Ca2+]i was completely inhibited when the extracellular solution was free of Ca2+. The V m response to hypotonic cell swelling was not attenuated in the presence of the L-type Ca2+ channel blockers nicardipine (n = 5), nifedipine (n = 5) and verapamil (n = 5) (all at 1 μmol/l). The data indicate that in rat mesangial cells, osmotic swelling induces a Ca2+ influx from extracellular space. This Ca2+ influx activates a Cl− conductance resulting in a depolarization of V m. The enhanced Cl− conductance may lead to KCl extrusion and hence regulatory volume decrease.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004240050055
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