Effects of H2-receptor antagonists on 3H-cimetidine binding and histamine-stimulation of cellular cAMP in isolated guinea pig gastric glands.
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概要
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<SUP>3</SUP>H-Cimetidine binding to plasma membranes of isolated guinea pig gastric glands was investigated, and the effects of five H<SUB>2</SUB>-receptor antagonists on <SUP>3</SUP>H-cimetidine binding and histamine stimulation of cellular cAMP were compared. Of the five cations tested, Cu<SUP>++</SUP> markedly increased specific <SUP>3</SUP>H-cimetidine binding. <SUP>3</SUP>H-Cimetidine had high affinity (K<SUB>d</SUB>=0.41×10<SUP>-6</SUP>M) and low affinity (K<SUB>d</SUB>=12.8×10<SUP>-6</SUP>M) binding sites. Cimetidine and etintidine were potent inhibitors of <SUP>3</SUP>H-cimetidine binding, while famotidine, ranitidine and TZU-0460 were not. Histamine stimulation of cellular cAMP was competitively inhibited by H<SUB>2</SUB>-receptor antagonists yielding pA<SUB>2</SUB> values of 6.41 for cimetidine, 6.82 for etintidine, 6.87 for ranitidine, 6.94 for TZU-0460 and 7.60 for famotidine. Because the K<SUB>B</SUB> value (log K<SUB>B</SUB>=-pA<SUB>2</SUB>) of 0.39×10<SUP>-6</SUP>M for cimetidine is close to the K<SUB>d</SUB> value for the high affinity <SUP>3</SUP>H-cimetidine binding site, it is presumed to represent a part of the H<SUB>2</SUB>-receptor, and the relative potency of etintidine against cimetidine in inhibiting <SUP>3</SUP>H-cimetidine binding is similar to that in inhibiting histamine stimulation of cellular cAMP. These results suggest that imidazole-derived H<SUB>2</SUB>-receptor antagonists (cimetidine and etintidine) and non-imidazole H<SUB>2</SUB>-receptor antagonists (famotidine, ranitidine and TZU-0460) compete with histamine at different sites on the H<SUB>2</SUB>-receptor of the gastric glands.
- 公益社団法人 日本薬理学会の論文
著者
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Tanaka Akira
The Third Department Of Internal Medicine Ehime University Medical School
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IBAYASHI HIROSHI
The Third Department of Internal Medicine, Faculty of Medicine, Kyushu University
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MISAWA Tadashi
The Third Department of Internal Medicine, Faculty of Medicine, Kyushu University
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NISHIHARA Shuichiro
The Third Department of Internal Medicine, Faculty of Medicine, Kyushu University
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- Effects of H2-receptor antagonists on 3H-cimetidine binding and histamine-stimulation of cellular cAMP in isolated guinea pig gastric glands.