EFFECTS OF ANGIOTENSIN II AND 1-SAR., 8-ISOLEU. ANGIOTENSIN II ON ELECTRICAL AND MECHANICAL PROPERTIES OF THE PORTAL VEIN FROM RATS OF DIFFERENT AGES
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概要
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The effects of angiotensin II (Ag-11) and 1-sar., 8-isoleu. angiotensin 11 (anti-Ag-11) on the membrane and mechanical properties of smooth muscle cells of the rat portal vein were investigated in three different age groups (6-8 weeks, immature rat; 3-5 months old, young rat and 13-15 months old, adult rat). Application of Ag-11 (10<SUP>-10</SUP> g/ml) did not depolarize the membrane, but did increase the spike frequency and potentiated the frequency and amplitude of twitch contraction. In a concentration of more than 10<SUP>-9</SUP> g/ml Ag-II, the membrane was depolarized and a phasic contracture was developed in three age groups. Depolarization of the membrane produced by Ag-II could be classified into two components, i.e. phasic and tonic depolarizations. In adult rats, Ag-II produced the highest amplitude of the depolarization in three age groups but tonic depolarization showed nearly the same amplitude as that observed in immature rats. These phenomena indicate that the sensitivity of smooth muscle cell membrane to Ag-II increases with age up to 3-5 months and that an increased sensitivity is accompanied by a generation of desensitization. Tachyphylaxis to Ag-II was also observed by repetitive applications, but the appearance depended on the stimulus conditions. Anti-Ag-II, itself slightly increased the spike frequency and the amplitude of twitch contraction. However, under pretreatment with anti-Ag-II (10<SUP>-9</SUP> or 10<SUP>-7</SUP> g/ml), the actions of Ag-II on the electrical and mechanical activities were markedly suppressed in the three age groups. When the dose-response curve was obtained from the mechanical response produced by Ag-II, the relation shifted to the right in the presence of anti-Ag-II in all age groups. In the presence of 10<SUP>-7</SUP> g/ml anti-Ag-II, no contracture was evoked by application of 10<SUP>-6</SUP> g/ml Ag-II in three age groups. Anti-Ag-II seems to possess a higher affinity to the angiotensin receptor than does Ag-II.
- 社団法人 日本薬理学会の論文
著者
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Takata Yutaka
Department Of Chemotherapy National Kyushu Cancer Center
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Kuriyama Hirosi
Department Of Pharmacology Faculty Of Medicine Kyushu University
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