| It is well known that the cellular swelling occurs when the cells are exposed to hyposmotic media. But all living cells seem to have some capacity to counteract this swelling by a mechanism that regulates the intracellular concentrations, so that the cells can control their normal volume. This mechanism is refered to as regulatory volume decrease (RVD). Many experiments have shown that the final results of RVD are that the effluxe of K~+ and Cl~- and the effluxe of organic osmolytes such as amino acid. Then water follows this efflux and the volume is controlled. Volume sensitive chloride channel regulates cell volume and stabilizes membrane potential in cell membrane. Recently, many studies indicated that cell membrane stretch could activate volume sensitive chloride channel in different cells, for example, volume sensitive chloride currents were activated by cell welling in cardiac ventricular myocytes and gastric myocytes in guinea-pig. Arachidonic acid (AA) is a unsaturated fatty acid in cell membrane, it is an important factor for changing membrane mobility. Up to now, it is not clear that volume sensitive chloride current is how to be modulated by unsaturated fatty acids in cell membrane.To investigate the effect of unsaturated fatty acids on volume-sensitive chloride current in antral circular myocytes of guinea-pig stomach, the whole cell patch-clamp technique was used in the myocytes isolated by collagenase. When the membrane potential was clamped at -60mV, the hyposmotic cell swelling activated volume-sensitive chloride currents (VSCC). The VSCC elicited by step pulse with 20mV intervals exhibited outward rectifier in I-V curve and time-dependent attenuation when membrane potential depolarized above +40mV. Arachidonic acid (AA) is a kind of unsaturated fatty acid with four double bonds. AA significantly inhibited VSCC in dose-dependent manner and the inhibitory effect was more significant on the part of time-dependent attenuation. Other unsaturated fatty acids (Linoleicacid, LA with twv, Uouble-bonds and Oleic acid, OA with one-double bonds) were also inhibited VSCC. The inhibitory potency of unsaturated fatty acids was AA > LA > OA. Saturated fatty acid, stearic acid(SA) didn't inhibit VSCC.In conclusion, exogenous unsaturated fatty acids inhibit VSCC and the inhibitory effect is more significant on the part of time-dependent attenuation. The inhibitory effects of exogenous unsaturated fatty acids are related to the number of double-bonds in fatty chain. |
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