ACUTE, ORAL ETHANOL ADMINISTRATION SUPPRESSES EPISODIC GROWTH-HORMONE SECRETION IN THE MALE-RAT

The effect of single dose ethanol administration on GH secretion was studied in young adult male rats bearing indwelling gastric and right-atrial cannulas. Rats (nonfasted) received saline or ethanol (1, 2, 3, or 4 g/kg) via gastric cannula 2 h before the onset of the daily dark period; blood was sampled every 15 min for 5 h. Each rat served as its own control, receiving saline and one ethanol dose separated by 2-3 days. Plasma samples were assayed for ethanol, GH, and testosterone. On saline days, all rats showed typical, episodic peaks of GH in plasma. This pattern was unaffected by ethanol at 1 g/kg (peak plasma ethanol approximate to 65 mg/100 ml). Ethanol at 2 g/kg caused a rapid, marked, but not total suppression of plasma GH levels (peak plasma ethanol approximate to 140 mg/100 ml), whereas at doses of 3 or 4 g/kg ethanol, a total suppression of GH secretion occurred (peak plasma ethanol 5 190 and 240 mg/100 ml, respectively). Plasma testosterone levels showed a similar dose-sensitivity to ethanol. The threshold for GH suppression appears to be around 100 mg/100 ml plasma ethanol and is sustained throughout the time period examined, despite falling ethanol levels.