Hemorrhage in DOC-salt hypertensive rats: plasma and platelet vasopressin

The effect of two consecutive hemorrhages, each 10% of blood volume, on plasma vasopressin concentrations was determined in conscious unilaterally nephrectomized Long-Evans rats made hypertensive by treatment for 3 wk with deoxycorticosterone (DOC) and substitution of 1% saline for drinking water (DOC-salt rats) or DOC alone (DOC rats) and in normotensive unilaterally nephrectomized rats drinking water (H2O rats) or saline (NaCl rats). In response to 20% hemorrhage, blood pressure decreased more (P less than 0.01) and plasma vasopressin increased less (P less than 0.01) in the DOC-salt rats than in the other groups. Under basal conditions, immunoreactive vasopressin was found in the platelets in NaCl, DOC, and DOC-salt rats (P less than 0.01) but not in H2O rats. Platelet vasopressin increased (P less than 0.05-0.01) in response to hemorrhage only in DOC-salt rats. In conclusion, the vasopressin response to hemorrhage in DOC-salt rats is impaired; platelet immunoreactive vasopressin is of little importance in normal rats but is increased by treatment with DOC and/or chronic salt loading; and platelet vasopressin increased in response to hemorrhage only in DOC-salt rats.