Effect of secretin on gastric parietal cell ultrastructure in man

The effect of secretin on parietal cell ultrastructure and on gastric mucosal potential difference have not been reported. In five healthy subjects, we studied the effect of intravenous injection of 2 clinical units per kg. of secretin on parietal cell canalicular and tubulovesicular membrane areas. In addition, we studied the effect of secretin on serum secretin levels and gastric mucosal potential difference. Biopsies of gastric mucosa for light and electron microscopy were obtained prior to and 15 and 30 minutes after secretin injection. Electron micrographs of 140 parietal cells were analyzed by the Loud quantitative method. Fifteen minutes following secretin administration, parietal cell canalicular membrane area decreased from a basal value of 4.37 +/- 0.43 per cent to 3.17 +/- 0.28 per cent (p less than 0.01). The number and length of microvilli also significantly decreased. Tubulovesicular membrane area increased from 9.32 +/- 0.7 per cent to 9.74 +/- 0.6 per cent (p greater than 0.05). The effect of secretin on canalicular membrane area was short lived, with recovery to nearly basal level at 30 minutes. Nuclear membrane area did not change at 15 and 30 minutes after secretin. After injection, serum secretin increased from a mean basal value of 15 to 2800 pg. per ml. at 15 minutes, falling to 130 pg. per ml. at 30 minutes. Gastric potential difference following secretin injection rose from -43 +/- 2 mv. to -54 +/- 2 mv. (p less than 0.01) within 10 minutes. In conclusion, a pharmacologic dose of secretin alters gastric parietal cell ultrastructure and causes significant elevation of gastric mucosal potential difference.