Mercury effects on the contractile activity of isolated heart muscle
| Autor: | Dalton Valentim Vassallo, E.M. Oliveira, J.J.F. Sarkis, José Geraldo Mill |
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| Rok vydání: | 1994 |
| Předmět: |
Male
medicine.medical_specialty Contraction (grammar) Calcium-Transporting ATPases Biology Toxicology Contractility Contractile Proteins Sarcolemma Internal medicine Caffeine medicine Animals Drug Interactions Rats Wistar Papillary muscle Pharmacology Dose-Response Relationship Drug Endoplasmic reticulum Myocardium Rana pipiens Papillary Muscles Myocardial Contraction Rats Sarcoplasmic Reticulum Endocrinology medicine.anatomical_structure Mechanism of action Toxicity Mercuric Chloride GRENOUILLE Female medicine.symptom Sodium-Potassium-Exchanging ATPase |
| Zdroj: | Toxicology and applied pharmacology. 128(1) |
| ISSN: | 0041-008X |
| Popis: | The toxic effects of HgCl 2 (1, 2.5, 5, and 10 μM) were studied in isolated, isometrically contracting rat papillary muscles and frog ventricular strips. In rat papillary muscles 1 μM Hg 2+ produced a small increase in the force of contraction. Higher concentrations of HgCl 2 produced a dose-dependent decrease in contractile force. The rate of force development was affected differently, increasing at 1 and 2.5 μM Hg 2+ and decreasing to control levels at 5 and 10 μM Hg 2+ . This was the result of a progressive reduction in the time to peak tension observed when HgCl 2 concentrations increased. This effect probably reflects the binding of Hg 2+ to SH groups inducing Ca 2+ release from the sarcoplasmic reticulum. The relative potentiation of postrest contractions was used as an index of sarcoplasmic reticulum activity. It was measured after pauses of increasing duration and was reduced at concentrations of 1 μM Hg 2+ when compared to that of the control. A further decrement in the relative potentiation was observed with higher Hg 2+ concentrations, indicating that the activity of the sarcoplasmic reticulum was depressed by mercury in a dose-dependent manner. Tetanic contractions were also studied in the rat myocardium. The tetanic tension did not change during treatment with 1 μM Hg 2+ hut decreased with 5 μM Hg 2+ , suggesting a toxic effect on the contractile proteins only at high Hg 2+ concentrations. Frog ventricu; lar strips were studied using the same HgCl 2 concentrations and no effects on either force or relative potentiation were observed. These findings suggest that Hg 2+ promotes dose-dependent toxic effects on heart muscle via actions on the sarcolemma, the sarcoplasmic reticulum, and contractile proteins. |
| Databáze: | OpenAIRE |
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