Episodic excretion of ethanol during chronic intragastric ethanol infusion in the male rat: continuous vs. cyclic ethanol and nutrient infusions.

Continuous intragastric infusion of ethanol has been reported to result in episodic daily blood alcohol concentrations in male rats (Tsukamoto et al., 1985). We have used a total enteral nutrition (TEN) model to study the effects of chronic alcohol exposure on blood and urine alcohol concentrations in adult male Sprague Dawley rats (300 g). Two TEN models were studied: 1) the continuous model in which a complete diet was infused i.g. for 24 h/day; or 2) the cyclic model in which TEN was infused intragastrically for 12 h/day (i.e., only during the dark phase of the lighting cycle). In the continuous model, blood alcohol concentrations (BACs) were determined at 0900 h each morning and were found to vary from day to day in an episodic fashion, with values ranging from less than 10 mg/dl to greater than 500 mg/dl. The urine alcohol concentrations (UACs) were also episodic and closely tracked those of serum, such that the 24-h UACs were excellent predictors of the BACs taken at 0900 h. Both BACs and UACs increased from values below 10 mg/dl to greater than 500 mg/dl, and then decreased back to below 10 mg/dl with a mean peak-to-peak interval of 6 +/- 0.9 days. In the cyclic model, daily UACs were also episodic (i.e., had a daily variation) and very closely resembled those of the continuous model. We have proposed that ethanol metabolism during experimental intragastric ethanol infusion in the rat occurs via a system characterized by time-dependent pharmacokinetics.