Neuroendocrine control of vasopressin secretion and its effect on blood pressure in subjects with spinal cord transection.

The osmotic and cardiovascular control of arginine vasopressin (AVP) secretion, and the effect of this hormone on cardiovascular regulation were assessed both in normal controls and in subjects with tetraplegia. Infusion of hypertonic saline caused a marked rise in blood pressure in the tetraplegics but not in the normal controls. Head-up tilt resulted in a greater AVP response in the tetraplegics than in the controls because of the additional hypotensive response in the tetraplegics. Infusion of AVP itself at physiological concentrations had little effect on blood pressure in the normal subjects but resulted in a marked rise in blood pressure in the tetraplegics. Tetraplegics therefore show appropriate release of AVP to both osmotic and cardiovascular stimuli but increased sensitivity to the pressor effects of this hormone.