不饱和脂肪酸在低渗牵张加强豚鼠胃窦平滑肌细胞毒蕈碱电流中的作用

利用全细胞膜片钳技术在急性分离的胃窦平滑肌细胞上记录离子电流的方法 ,探讨外源性不饱和脂肪酸是否参与低渗牵张加强毒蕈碱电流的过程。在豚鼠胃窦平滑肌细胞上膜电位被钳制在 - 2 0 0mV等渗状态时 ,5 0 μmol/L卡巴胆碱 (carbachol,CCh)引起的毒蕈碱电流 (ICCh)作为对照 ,发现低渗牵张可以使ICCh明显增加到对照的 2 2 6 0±2 1 0 %。当用含 5 μmol花生四烯酸 (arachidacid ,AA)、亚麻酸 (linoleicacid ,LA)或亚油酸 (oleicacid,OA)细胞外液灌流时 ,ICCh分别被抑制在对照的 3 8± 0 6%、3 5 2± 0 8%和 66 6± 0 6%。在这种情况下 ,低渗牵张刺激可以使ICCh分别增加到 10 6 0± 2 5 %、173 2± 6 8%和 2 2 2 1± 11 0 %。 5 μmol/LAA抑制低渗牵张增加的毒蕈碱电流 5 1 2± 3 8% ,而在等渗状态下抑制ICCh为 96 2± 1 6%。上述结果提示 ,不饱和脂肪酸中双键数目越多 ,抑制效应越强 ;但不饱和脂肪酸不参与低渗刺激加强毒蕈碱电流的过程。

Role of unsaturated fatty acids in the enhancement of muscarinic current by hyposmotic membrane stretch in guinea pig smooth muscle cells

To investigate the function of exogenous unsaturated fatty acids in hyposmotic membrane stretch enhancement of muscarinic current (ICCh) in antral circular smooth muscle cells of guinea pig, we recorded the membrane current with the conventional whole cell patch-clamp technique. ICCh elicited by 50 μmol/L carbachol (CCh) at the holding potential of -20 mV under isosmotic condition was taken as control. Hyposmotic membrane stretch increased ICCh to 226.0±21.0%. When the cells were pretreated with 5 μmol/L arachidonic acid (AA), linoleic acid (LA) or oleic acid (OA), ICCh was inhibited to 3.8±0.6%, 35.2±0.8% and 66.6±0.6% respectively. Hyposmotic membrane stretch increased ICCh to 106.0±2.5%, 173.2±6.8% and 222.1±11.0% of the control respectively. Five μmol/L AA inhibited hyposmotic membrane stretch-enhanced ICCh by 51.2±3.8%, while the control ICCh under isosmotic condition was inhibited by 96.2±1.6%. The results suggest that unsaturated fatty acids inhibited ICCh and the inhibitory effect is more significant when the unsaturation degree is increased. However, the unsaturated fatty acids are not involved in the increase of ICCh induced by hyposmotic membrane stretch.