MECHANOSENSITIVE SINGLE-CHANNEL CALCIUM CURRENTS IN RAT MESANGIAL CELLS

Mechanical stimulation of mesangial cells enhances expression of early response protooncogenes is an extracellular Ca2+-dependent manner. Th is has lead investigators to postulate that a mechanosensitive Ca2+ ch annel may exist in these cells. At the present time, however, very lit tle is known about single channel Ca2+ currents in mesangial cells. To examine this question, cell-attached patches of rat mesangial cells i n early passages were studied with 100 mM BaCl2 patch-clamp pipets. Ou r studies identified a 21 pS, Co2+-sensitive channel that responded wi th an increase in open probability to mechanical stretch, applied thro ugh the patch pipet. The channel was also activated by a reduction in extracellular osmolarity. In both instances, channel responses underwe nt spontaneous adaptation despite continuous stimulation. This Ca2+ ch annel exhibited electrophysiological and kinetic properties that disti nguished it from other cation-selective channels previously reported b y us and other investigators on rat mesangial cell membranes. (C) 1994 Academic Press, Inc.