Effects of prenatal alcohol exposure on forepaw digit length and digit ratios in rats.

Prenatal exposure to alcohol can cause limb and digit defects. Variations in digit ratios in humans are associated with prenatal testosterone exposure. Since prenatal alcohol can reduce testosterone in rats, the effects of prenatal alcohol were measured on rat digit length. Pregnant Sprague-Dawley rats were intubated with 0 g/kg, 4 g/kg, or 6 g/kg of ethanol from Gestational Day 8 (GD8) to GD20. The 0-g/kg group and a nonintubated group served as controls. At postnatal day 31, forepaw digit lengths were measured and digit ratios calculated. Females had smaller digits on both forepaws and higher digit ratios on the right forepaw than males. Rats exposed to 6 g/kg of ethanol had smaller digits than controls on both forepaws and higher digit ratios than controls on the left forepaw. Rat digit ratios differ between the sexes, and prenatal alcohol exposure affects digit ratios. The results are consistent with a perinatal disruption of testosterone levels by alcohol and/or of testosterone's effects on digit length and ratios. An alternate interpretation is consistent with a retinoic acid-mediated effect of alcohol on digit length and ratios.