ArticleNaunyn-Schmiedeberg's archives of pharmacology1994
Calcium dependency of the AT1-receptor mediated effects in the rat portal vein: influence of calcium antagonists.
Article in Naunyn-Schmiedeberg's archives of pharmacology, 1994. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
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0 citing papers in PubMed, 6 citations in OpenAlex.
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5 authors at 2 institutions in 2 countries.
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No grant is acknowledged in the PubMed record.
Abstract
The calcium dependency of AT1-receptor mediated contractions was studied in isolated rat portal vein preparations. The spontaneous phasic contractile force of the rat portal vein was increased (ED50 = 1.76 mmol/l) and the frequency of contractions decreased by raising the extracellular calcium concentration. The Ang II-induced rise in phasic contractile force (mediated by AT1-receptors, Zhang et al. 1993) proved most pronounced at 0.9 mmol/l of calcium chloride, but it was weaker at either lower or higher calcium concentrations. The maximal increases in the phasic contractile force induced by Ang II were 2.4 +/- 0.4, 14.8 +/- 0.9 and 5 +/- 0.5 mN at calcium concentrations of 0.5, 0.9 and 2.5 mmol/l, respectively. Calcium antagonists reduced at the lower and abolished at the higher concentrations (nifedipine 2 x 10(-8) or 10(-7) mol/l; verapamil 10(-7) or 5 x 10(-7) mol/l; diltiazem 3 x 10(-7) or 10(-6) mol/l) the spontaneous contractile force. All of these calcium antagonists caused a strong inhibition or suppression of the phasic contractions induced by Ang II. The rank order of potency was nifedipine > verapamil > diltiazem. Ang II (10(-6) mol/l) elicited a tonic contraction which was abolished by the AT1-receptor antagonist losartan 10(-6) mol/l but not by the AT2-receptor antagonist PD 123177 (10(-5) mol/l). Very high concentrations of nifedipine (10(-6) mol/l), verapamil (5 x 10(-6) mol/l) and diltiazem (5 x 10(-6) mol/l) almost suppressed the tonic effect evoked by the activation of AT1-receptors. In a nominally Ca2+ "free", EGTA-containing solution, a single supra-maximal concentration of Ang II (10(-6) mol/l) caused a transient contraction, also mediated by AT1-receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
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