Rat brain microsome fluidity as modified by prenatal ethanol administration.

The fluorescence anisotropy (r) of diphenylhexatriene (DPH) and of trimethylamino-diphenylhexatriene (TMA-DPH) as a function of temperature (10 degrees to 54 degrees C) was measured in brain microsomes of newborn rats prenatally exposed to ethanol. In this temperature range, the relationship between r and T was linear. The addition of ethanol in vitro to microsomal suspensions influenced the slope of the line of r versus T only when DPH was used as a probe and with high concentrations of the alcohol (> or = 0.3 M). The administration of ethanol (18% of total energy intake) in vivo to pregnant dams affected the slope of the lines of r versus T of the microsomes of pups, either using DPH or TMA-DPH as probes. The slope was also affected in brain microsomes obtained from dams, yet, only with TMA-DPH and in the opposite sense than in pups. We conclude that the effect of prenatal exposure to ethanol depended on metabolic alterations induced by the alcohol and not on its detergent properties for the following reasons: (a) The effects in vitro and in vivo were different and (b) in vitro effects could be obtained only with high concentrations (> or = 0.3 M), whereas in vivo effects were produced by small doses of ethanol. Besides, the effects of the administration of the alcohol in vivo were different in adult and intrauterine life.