Inhibitory effect of alcohol on cyclic GMP accumulation in human platelets

[Effect of ethanol on platelet biology]

In recent years, interest in the study of platelets, significantly increased due to recent discoveries providing convincing evidence that their functions by are not limited to their participation in the blood coagulation mechanism. Many works are devoted to the study of the functional state of platelets under conditions of acute and chronic alcohol exposure. The results of such studies can be useful for the development of new markers of the degree of alcohol intoxication of the body for the subsequent choice of the method drug correction of disorders caused by acute or chronic alcohol effects. The review summarizes results in vivo and in vitro of studies performed during more than 60 years on the effect of ethanol on the biogenesis, number, morphology and biochemistry of platelets.

Peri-operative decreased cAMP levels in long-term alcoholic patients

Long-term alcoholic patients have a five-fold higher risk of post-operative bleeding complications compared with nonalcoholic individuals. Serotonin increases and cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) decrease platelet aggregation. We examined the platelet-rich plasma levels of these substances and agonist-induced platelet aggregation in long-term alcoholic patients before and after surgery. Thirty-three consecutive patients (13 long-term alcoholics and 20 non-alcoholics) scheduled for tumour resections of the upper digestive tract were included in the study. The levels of cAMP were significantly decreased before and after surgery in long-term alcoholic patients, but there were no significant differences in cGMP and serotonin levels in alcoholic compared with non-alcoholic patients. In contrast to previous studies, no significantly altered aggregation responses in long-term alcoholics were found. A possible explanation is decreased inhibition through diminished cAMP levels; cGMP and serotonin do not seem to influence peri-operative haemostasis.

Effects of ethanol and other constituents of alcoholic beverages on coronary heart disease: a review

Moderate consumption of alcoholic beverages has been shown to reduce the incidence of coronary artery disease (CAD) compared to abstinence and heavy drinking. Epidemiologic studies suggest that any form of alcoholic beverage offers this protection. However, several studies have shown that the polyphenolic compounds found in many alcoholic beverages are more effective than pure alcohol for improving specific biologic factors known to contribute to atherosclerotic development. The alcoholic beverage polyphenols improve endothelial function, protect LDL from oxidation, inhibit platelet activity, inhibit vascular smooth muscle cell (VSMC) proliferation and migration, and reduce the activation of monocytes in the post-prandial period. Not only does pure alcohol not provide these benefits, but it has also been shown to act as a pro-oxidant, impair endothelial function, and possibly be proinflammatory. In studies comparing red wine, white wine, beer, and liquor, the red wine and dark-colored beer seem to provide more protection than liquor, even though the alcohol contents (per serving) are similar. The results suggest that the type of alcoholic beverage consumed does make a difference because pure alcohol cannot fully account for the beneficial effects.

Alcohol intoxication and withdrawal: the role of nitric oxide

Nitric oxide is an important messenger in the central nervous system and several types of evidence suggest that it mediates various alcohol effects. Treatment with a nitric oxide synthase inhibitor enhances the acute central depressant or anesthetic effect of alcohol and decreases some stimulatory effects of alcohol withdrawal after chronic alcohol treatment. Conversely, treatment with a nitric oxide donor inhibits the anesthetic effect of alcohol, blocks the effect of the nitric oxide synthase inhibitor on alcohol anesthesia, and enhances the severity of some alcohol withdrawal signs. These results indicate that changes in nitric oxide synthesis mediate some aspects of alcohol intoxication and withdrawal and that nitric oxide systems represent an important therapeutic target for the development of agents to treat alcoholism and alcohol intoxication.

Inhibition of platelet aggregation in whole blood after exposure of rats to alcohol by inhalation

The dose-effect relationship between blood alcohol concentration (BAC) and altered platelet function was examined in whole blood in a rat model of alcohol exposure by inhalation, using the impedance method of ex vivo whole blood platelet aggregation. With rates of alcohol addition to the chamber air inflow from 29 to 56 mg ethanol/l air/min, BAC was dependent on duration of exposure and concentration of alcohol in the air. Next, 3, 6, and 9 h exposures to the highest delivery rate were used, and platelet aggregability was tested. After 9 h, BAC reached 453 +/- 16 mg% and aggregation responses to three doses of collagen were significantly lower than in control blood (p < 0.01). Less consistent inhibition was observed with arachidonic acid and ADP, and also when exposure duration was reduced. However, some significant inhibition of collagen-induced aggregation (p < 0.05) was observed with BAC as low as 127 +/- 15 mg%. These experiments demonstrate that in vivo alcohol exposure inhibits, in a concentration-dependent manner, ex vivo rat whole blood platelet aggregation, at BACs readily attained in humans by ingestion.