The distribution and metabolism of acetaldehyde in rats during ethanol oxidation—I: The distribution of acetaldehyde in liver, brain, blood and breath

Abstract

An in vivo investigation was made of the distribution of acetaldehyde (AcH) during ethanol metabolism. Different doses of ethanol were administered orally to male and female Sprague-Dawley rats ( n = 96) and AcH measured at various times thereafter in the liver, blood, brain and breath. The results showed that the liver was the primary site for the oxidation of the ethanol-derived AeH. Only a small amount of the total AcH formed in this organ escaped into the rest of the body, but this amount increased with increased hepatic ethanol concentration. The hepatic AcH level was higher in male rats than in females with the same hepatic ethanol concentration. The extrahepatic AcH levels in arterial cerebral and in peripheral tail blood correlated well with the corresponding hepatic AcH levels. The bulk of the hepatic AcH output was eliminated extrahepatically, thus drastically changing the AcH level from that initially leaving the liver. Sex differences also appeared in the extrahepatic blood AcH levels, with the female rats displaying higher AcH levels, as a result of their less efficient extrahepatic AcH elimination. The peripheral tail blood AcH was found to be similar to the AcH level of the venous blood before the hepatic blood AcH is added to it. Regardless of the AcH levels in the liver and blood, no AcH was found in the brain. Less than 5 per cent of the hepatic AcH output was exhaled. Pentobarbital anaesthesia strongly depressed the amount of AcH exhaled. The AcH in the breath did not reflect the hepatic AcH as well as the blood AcH levels did.