Effects of omeprazole and pirenzepine on enterochromaffin-like cells and parietal cells in rat stomach.
OBJECTIVE
The purpose of this study was to investigate the mechanism of the regulation of histamine synthesis in enterochromaffin-like cells, chemically and structurally, by treatment with omeprazole and pirenzepine.


METHODS
The ultrastructures of enterochromaffin-like cells and parietal cells were examined in rats treated with oral omeprazole (20 mg/kg) or intraperitoneal pirenzepine (1 mg/kg) administration. Serum gastrin concentrations, mRNA levels of H+-K+-ATPase and histidine decarboxylase, and the fundic concentrations of somatostatin and histamine were determined.


RESULTS
Pirenzepine treatment suppressed omeprazole-induced increases in serum gastrin levels and mRNA levels of H+-K+-ATPase and histidine decarboxylase. Pirenzepine also decreased omeprazole-induced increases of histamine concentration in fundic mucosa. Pirenzepine elevated somatostatin mRNA level, previously decreased by omeprazole treatment, in fundic mucosa. In the cytoplasm of enterochromaffin-like cells, omeprazole markedly reduced the numbers of vesicles and granules, but significantly increased their diameters, whereas pirenzepine treatment changed neither of these features. The densities and diameters of both vesicles and granules produced by treatment with omeprazole and pirenzepine were between those produced by treatment with omeprazole alone and pirenzepine alone.


CONCLUSIONS
Omeprazole-induced hypergastrinemia and pirenzepine-induced somatostatin synthesis play important roles not only in histamine synthesis but also in ultrastructural changes in enterochromaffin-like cells.
Tari
A
A
Department of Internal Medicine, Hiroshima Red Cross Hospital and Atomic-bomb Survivors Hospital, Japan.
Kuruhara
Y
Y
Yonei
Y
Y
Yamauchi
R
R
Okahara
S
S
Sumii
K
K
Kajiyama
G
G
D000818:Animals; D000897:Anti-Ulcer Agents / Q000627:therapeutic use*; D015152:Blotting, Northern; D004359:Drug Therapy, Combination; D019861:Enterochromaffin-like Cells / Q000187:drug effects*; D017506:H(+)-K(+)-Exchanging ATPase / Q000187:drug effects; D006632:Histamine / Q000097:blood; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D008297:Male; D009853:Omeprazole / Q000627:therapeutic use*; D010295:Parietal Cells, Gastric / Q000187:drug effects*; D010890:Pirenzepine / Q000627:therapeutic use; D012333:RNA, Messenger / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013270:Stomach / Q000737:chemistry / Q000166:cytology* / Q000187:drug effects*
D000897:Anti-Ulcer Agents; D012333:RNA, Messenger; D010890:Pirenzepine; D006632:Histamine; D017506:H(+)-K(+)-Exchanging ATPase; D009853:Omeprazole