Arginine vasopressin and body fluid homeostasis in the fetal alcohol exposed rat.

Studies involving fluid homeostasis were carried out in adult Long-Evans rats born to mothers given liquid diets containing 35% of the calories derived from ethanol and compared to offspring of dams given isocaloric liquid diets containing no ethanol. Plasma levels of arginine vasopressin (AVP), plasma and urine osmolality, and urine production were determined in water-sated and water-deprived offspring. In the water-sated condition, the group exposed to alcohol prenatally had plasma levels of AVP seven-fold above control levels. This increase was associated with a large increase in within-group variability. Water consumption was also significantly elevated in the group of fetal alcohol exposed (FAE) rats. Plasma and urine osmolality and urine production were similar to control levels. In the control animals, 24-hr of water deprivation produced the expected increase in AVP, in plasma and urine osmolality, and decrease in urine production. The FAE animals, however, showed parallel changes in plasma and urine osmolality and urine production with no significant change in AVP. Examination of basal glucose metabolic rates in the cerebral structures involved in fluid homeostasis revealed that despite the large increase in AVP levels in the FAE rats, only the neurohypophysis and supraoptic nuclei showed significant increases in activity. These data suggest that fetal alcohol exposure causes a long-term disruption in the central mechanisms regulating vasopressin release and fluid homeostatic responses.