Experimental Studies on Carbonic Anhydrase Activity in the Gastric Mucosa and on the Fine Structure of the Parietal Cell

Abstract

In an attempt to solve a function of the gastric secretion, experiments were made chiefly on the changes of carbonic anhydrase (hereinafter referred to as C. A.) activity and that of the fine structure of the parietal cell, through the administration of various medicaments efficacious against either stimulating or inhibiting the secretion of gastric juice. The experiments also included the influences observed on the intra-mucosa clectrolytes (Na⁺, K⁺, Cl^-), intra-juice electrolytes, and blood C. A. activity, with thefollowing findings:
1) The medication of Histamine dihydrochloride intensified the gastric C. A. activity of rats; in the fine structure of parietal cell the mitochondria became ramified and enlarged; the vesicles diminished in number and gathered around the intra-cellular canaliculi; the intracellular canaliculi developed and were choked completely with the grown microvilli.
2) Following the administration of Acetazolamide, the gastric C. A. activity decreased significantly. Even when it was used together with Histamine, no effect of histamine was observed whatsoever. In the fine structure of the parietal cell, the vesicles enlarged with a remarkable increase in number. The intra-cellular canaliculi became indistinct, and the microvilli diminished in size. These findings, together with the decreased secretion of gastric juice, can be considered as an important factor in solving the function of gastric secretion.
3) The activation of the gastric C. A. activity of dogs was approximately seven times high in the courpus region, as compared to that of the pyloric region. This finding, together with the observation of the variations in the gastric C. A. activity and the changes in the fine structure of the parietal cell, caused by the medication of Histamine and Acetazolamide, strongly suggests that the gastric C. A. has some relations with the parietal cell.
4) With the use of Chlormerodrin, the gastric C. A. activity of rats showed a certain decline; however, its effect was much lesser than that of Acetazolamide. In the fine structure of the parietal cell, the mitochondria became diminished, while the cristae mitochondriales were found dense and the electron density of the mitochondria matrix was high. Therefore, the finding also suggests the presence of a definite relationships between the succinic dehydrogenase and the mitochondria.
5) When Atropine was administered, no variations in the gastric C. A. activity of rats were observed. When used together with Histamine, the C. A. activity by Atropine was lower than that of the sole use of Histamine. In the fine structure of the parietal cell, no changes other than the increase in the vesicles was observed. When Histamine was used together, its influence had not existed. During the course of the observation, a definite relationship between the gastric C. A. activity and the fine structure of the parietal cell apprently existed.
6) Upon administration of Prednisolone and Urethane, there was no varietions in the gastric C. A. activity of rats; however, when Histamine was used together with the foregoing medicaments, the C. A. activity increased. In the fine structure of the parietal cell, it is observed that the Prednisolone decreased the vesicles and the expansion of the intracellular canaliculi, the elongation of the microvilli, and the swelling of their tips. The administration of Urethane alone produced no change.
When used together with Histamine, it produced similar changes in the vesicles and the intra-cellular canaliculi, as caused by the sole use of Histamine, and showed similar vicissitudes of the C. A. activity.
7) Following the administration of Ouabain there observed no changes in the gastric C. A. activity of rats. However, when used together with Histamine, it resulted in lower activation than that of the sole medication of Histamine, and the depression of the gastric acid secretion.