Sodium-induced elevation of blood pressure in the anephric state

Normotensive anephric rats infused with 2 milliliters of a hyperosmolar solution of either sodium chloride or mannitol showed an increase in arterial pressure that was very pronounced with the sodium chloride and that could be partly abolished by administration of an antagonist to the vasopressor action of antidiuretic hormone (ADH). Rats with congenital ADH deficiency subjected to the same treatment showed smaller increments in arterial pressure that remained unchanged after administration of the ADH antagonist. Expansion of intravascular fluid volume was similar in all four groups and bore no correlation to the change in arterial pressure. It is concluded that about half of the increase in blood pressure induced by saline was attributable to the vasopressor effect of stimulated ADH and the remainder to an additional sodium-related factor, since it was more pronounced in the saline-infused than in the mannitol-infused groups. Expansion of the intravascular volume per se could only account for a minimal part of the increment in pressure.