Antioxidants prevent depletion of [Mg2+]i induced by alcohol in cultured canine cerebral vascular smooth muscle cells: possible relationship to alcohol-induced stroke

Synergistic effects of ethanol and hyperthermia on carotid artery vasoconstriction

BACKGROUND

Heatstroke is a serious condition and clinical studies indicate that vascular stroke increases with excessive consumption of alcohol (ethanol). It was our objective to test the influence of ethanol on cerebral perfusion at normal and higher temperatures.

METHODS

Recording of isometric tension in rabbit carotid artery strips in organ baths with different concentrations of ethanol at 37 degrees C and during hyperthermia (39-43 degrees C) and scintigraphic cerebral imaging of a radioactive isotope in the control situation and during hyperthermia.

RESULTS

Stepwise heating induced reproducible reversible graded contraction, proportional to temperature. At high concentrations (toxic levels), ethanol induced an increase in tension and heating potentiated these responses. Extracellular Mg(2+) potentiated both heat-induced contraction and ethanol-induced contraction while extracellular Ca(2+) had no effect on these responses. During hyperthermia and ethanol scintigraphic isotope uptake was reduced in cortical and cerebellar regions.

CONCLUSIONS

Carotid artery vasomotor tone is temperature dependent and heating induces vasoconstriction. Alcohol (ethanol) at 37 degrees C elicited carotid artery contraction at high concentrations (toxic levels) but at any concentration during elevated temperature (39-43 degrees C). Ethanol potentiated the effect of hyperthermia-induced vasoconstriction and reduced cerebral perfusion as shown by radionuclide imaging. The synergistic effect of ethanol and hyperthermia may induce heat stroke and brain damage.

Antioxidants prevent ethanol-induced contractions of canine cerebral vascular smooth muscle: relation to alcohol-induced brain injury

The present study was designed to test the hypothesis that alpha-tocopherol (Vit. E) and pyrrolidine dithiocarbamate (PDTC) might exert direct effects on alcohol-induced contractions of canine basilar cerebral arteries. After precontraction of arterial ring segments with ethanol, PDTC (10(-8)-10(-6) M) and Vit. E (10(-6)-10(-4) M) induced concentration-dependent relaxations of cerebral arteries, compared to untreated controls. The effective concentrations producing approximately 50% of the maximal relaxation responses (EC(50) values) were about 2.48+/-0.09 x 10(-7) M for PDTC, and 1.87+/-0.10 x 10(-5) mM for Vit. E, respectively. Preincubation of these arterial rings with EC(50)'s of PDTC or Vit. E for 40 min attenuate markedly the contractions produced by alcohol, at concentrations of 1-400 mM. However, both PDTC and Vit.E do not relax equi-potent precontractions induced by either KCl or prostaglandin F(2alpha) (PGF(2alpha)) or inhibit their contractions. These data suggest that alcohol-induced contractions of cerebral arteries are mediated via excitation-contraction coupling pathways different from those used by KCl or receptor-mediated agonists such as PGF(2alpha). The present results, when viewed in light of other recently published data, suggest that antioxidants may prove useful in the amelioration and treatment of alcohol-induced brain damage and strokes.