Effects of hemorrhage on vasopressin secretion and arterial blood pressure during experimental diabetes insipidus in goats.

The effect of hypotensive hemorrhage on plasma vasopressin (AVP) concentration and carotid blood pressure before and after induction of experimental diabetes insipidus (DI) was studied in the conscious goat. Bleeding to the point of blood pressure fall (blood loss 15-25% of the estimated blood volume) caused an immediate, approximately hundred fold, increase in the plasma AVP concentration in the normal animal. Hemorrhage to the same extent during DI did not affect the plasma AVP levels. A rather transient hypotensive response to bleeding was seen before disruption of the pituitary stalk, but during DI the recovery of the hemorrhage-induced hypotension was less effective. However, the normalization of the blood pressure after bleeding was slightly more efficient during the permanent than during the temporary phase of DI. It is concluded that an intact hypothalamo-neurohypophysial connection is necessary for the massive release of AVP normally seen in response to hypotensive hemorrhage. It is also confirmed that the lack of this hormonal response to bleeding is accompanied by an increased susceptibility to the hypotensive effect of hemorrhage.