Detection of a CA repeat polymorphism in the rat class I alcohol dehydrogenase gene.

Differences in the amount of alcohol dehydrogenase (ADH) expressed in liver could play a role in altering ethanol metabolic rates and thus influence alcohol consumption. There is an alternating purine-pyrimidine repeat length polymorphism in the first intron of mouse Adh-1. Mouse strains that lack 101 basepairs of this 288 basepairs alternating sequence express only half as much ADH mRNA and have lower ADH-A2 activity, suggesting that this alternating sequence might modify transcription of the gene. The rat class I ADH gene also has a CA repeat in the first intron. A polymerase chain reaction (PCR) method was used to amplify the CA repeat region in different rat lines to determine whether this CA repeat is polymorphic in the rat and if so, if different length repeats correlate with the drinking behavior of rats selectively bred for high [preferring (P); high alcohol drinking (HAD); Alko, Alcohol (AA) lines] and low [non-preferring (NP); low alcohol drinking (LAD); Alko, Non-Alcohol (ANA) rat lines] alcohol drinking. A CA repeat polymorphism was detected in rat class I ADH of these different rat lines, but there was no difference in the length of the repeat between the high and low drinking rats in each line. Liver ADH activity was also not significantly different between two rat lines that have different CA repeat lengths. Thus, there is CA repeat length polymorphism in the first intron of rat class I ADH, which may be useful in genomic mapping, but it is not associated with differences in ADH activity or drinking behavior in these rat lines.