The influence of saline loading on renal glucose reabsorption in the rat.

Glucose titration studies were performed in normal rats under control conditions and during expansion of the extracellular fluid volume. In association with expansion, the maximal rate of glucose transport (Tm(glucose)) decreased while glomerular filtration rate (GFR) typically increased; thus there was a consistent increase in the GFR/Tm(glucose) ratio. In previous studies, marked reduction of the nephron population was associated with an alteration in the kinetics of glucose transport and GFR/Tm(glucose) ratios were observed to increase. In both volume-expanded rats and in animals and human beings with uremia, the splay in the titration curve is increased. Finally in both volume-expanded animals and uremic animals fractional reabsorption of sodium is depressed. One interpretation of the present data is that the natriuretic "third factor" may influence a key rate-limiting step in glucose transport; and it is possible that this step is shared by or coupled to a rate-limiting step in sodium transport.