Corticosteroids and plasma restitution after hemorrhage and hypothalamic lesions.

The effects of electrolytic ablation of the anteroventral portion of the third ventricle (AV3V) on plasma volume (PV) restitution and adrenal corticosteroid responses after hemorrhage were determined. After recovery from AV3V ablation or control surgeries, animals were implanted with a catheter in the femoral artery. PV was determined before and either 2 or 24 h after moderate hemorrhage (1.4% body wt for controls; 1.3% body wt for AV3V lesion) by calculating dilution of 125I-labeled serum albumin. Other rats with AV3V lesions and control animals were used to measure concentrations of renin, aldosterone, and corticosterone 0.5 or 2 h after similar hemorrhage. The percent of shed PV restored was similar in rats with AV3V lesions and control-operated animals both 2 and 24 h after hemorrhage. Furthermore, the restitution of plasma protein mass was not different. Rats with AV3V lesions showed a similar increase in plasma renin concentration after hemorrhage, but they showed a smaller increase in the concentration of plasma aldosterone and no increase in the concentration of plasma corticosterone. These data demonstrate that electrolytic ablation of AV3V periventricular tissue does not alter either the short- or long-term phase of PV restitution, even though concentrations of plasma corticosterone are not increased.