RECENT ADVANCES REGARDING PARIETAL CELLS OF STOMACH

During the last five years the recognition of ionic channels in the parietal cells of stomach and acid chloride mechanisms of secretion by these cells has become totally clear by the "Patch Oamp" technique. The apical cytoplasm in the oxyntic cells are in the form of vesicles where membranes contain H, K -ATPase pump. Stimulation causes fusion of these tubular vesicles with the cell membran of the apical region and this process increases the cell membrane area to about 10 times. Associated with this process is the activation and opening of the channel of chloride and potassium in the apical membrane. After the stimulation of cell a considerable amount of chloride passes through the activated vesicles thus producing cannaliculi secretion of acid associated with the hyperpolarization of the membrane of the apical region. This process also transport considerable amount of chloride and also presumably opens the cannaliculi several folds. At present the acceptable model-of transport in apical cell membrane of the parietal cells is based on the counter transport of chloride and potassium. Thus during stimulation, fusion of vesicles in the apical membrane and expansion of apical membrane leads to opening of hydrogen-potassium pump into the lumen of the gland. The hyperpolarization of the membrane of the apical region is associated with the secretion of acid.