Thallium is an environmental contaminant linked to cardiovascular disorders.
Previous studies on thallium's cardiac effects used concentrations exceeding intoxication levels, yielding conflicting data.
Purpose of the Study:
To investigate the effects of thallium on myocardial contractility across a range of environmentally relevant and intoxication-level concentrations.
To clarify the dose-dependent and time-dependent effects of thallium on cardiac muscle function.
Main Methods:
Isolated sheep interventricular cordis muscles and guinea pig papillary muscles were exposed to varying thallium concentrations (10⁻⁸ to 10⁻³ M).
Contractile force was measured under different stimulation frequencies (0.1–2.0 Hz) and rest periods.
Effects were analyzed concerning time, thallium concentration, and stimulation rate.
Main Results:
Thallium exposure resulted in varied responses: persistent contractility increase (15%), progressive loss of contractile force (50%), or a combination.
Higher thallium concentrations and stimulation rates accelerated the decay of contractile force.
Thallium significantly impacted cardiac muscle function, particularly after rest periods, suggesting slow inward current involvement.
Conclusions:
Thallium exerts complex, concentration-dependent effects on myocardial contractility.
The findings highlight thallium's potential to induce cardiac dysfunction at environmentally relevant levels.
Further research into the mechanisms, including slow inward current modulation, is warranted.