Untersuchungen zur Wirkung von Angiotensin II auf einen autorhythmischen glatten Gefäßmuskel (Pfortader der Ratte)

Voth, D.; Agsten, M.; Schipp, R.; Lübcke, H.

doi:10.1007/bf02123261

Cited by 5 publications

(1 citation statement)

References 28 publications

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“…However, this conclusion concerning the relationship between drug sensitivity and aging may not be generalized, because in the rabbit mesenteric artery the sensitivity of smooth muscle membranes to acetylcholine (hyper polarizing action) declined gradually with aging (14). Some investigators (3,6,18) ruled out the generation of tachyphylaxis of excitatory response to Ag-II in the portal vein. On the other hand, Shepherd and Van Houtte (19) reported a controversial conclusion that tachyphylaxis appeared on the rat portal vein by treatment with Ag-II.…”

Section: Discussionmentioning

confidence: 99%

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

Takata

Kuriyama

1979

Japanese Journal of Pharmacology

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Abstract-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-I1 (10-10 g/ml) did not depolarize the membrane, but did increase the spike frequency and potentiated the frequency and amplitude of twitch contraction. In a concen tration of more than 10-9 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 depolari zation 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. Tachy phylaxis 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 (10-9 or 10-7 g/ml), the actions of Ag-II on the electrical and mechanical ac tivities 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 10-7 g/ml anti-Ag-II, no contracture was evoked by application of 10-6 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.Excitatory actions of angiotensin 11 (Ag-11) on the mechanical or electrical activity of various visceral smooth muscles have been investigated [taenia coli of the guinea-pig (1, 2), mesenteric veins of the rabbit and dog (3), and the rat myometrium (4, 5)], and this agent consistently depolarized the membrane and increased the spike frequency. Carruba et al.(4) studied the Ag-11 action on the contraction of isolated rabbit, guinea-pig and rat portal veins, and concluded that Ag-11 proved to be the most active drug on the rat portal vein but exhibited only a slight increase in mechanical activity of the guinea-pig and rabbit pre parations. Weston and Golenhofen (6) also reported that Ag-11 produces an excitatory action on the rat and rabbit portal veins but that it showed an inhibitory action on the guinea-pig portal vein. These results suggest the species differences of Ag-11 actions. It

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Section: Discussionmentioning

confidence: 99%