Long-term measurement of total exchangable sodium in one- and two-kidney Golblatt rats.

Total exchangeable sodium (Nae) was measured by wholebody counting of 22Na in 1- and 2-kidney Goldblatt rats before, and for 12 weeks after, renal artery clipping. In 1-kidney Goldblatt rats, Nae relative to body weight increased immediately after the clipping procedure and then fell though not to normal levels; from the 10th to the 12th week it again rose rapidly, probably secondary to vascular damage. In 2-kidney Goldblatt rats, Nae relative to body weight increased immediately after the clipping procedure but by the 5th day it was back to normal and remained normal thereafter. Consideration of the values for absolute Nae (i.e. expressed in mmol per rat) casts some doubt on the reality of the sodium 'retention', except in the 1-kidney Goldblatt rats in the later stages of their hypertension. Immediately after surgery temporary loss of weight (presumably mainly affecting fat stores and muscle) probably accounts for much of the rise in Nae relative to body weight.