The effects of Ringer-Locke or blood infusions on the lateral intercellular spaces of the rat proximal tubule.

Diuresis and natriuresis follow volume expansion by intravenous infusion of either blood or saline. However, the mechanisms underlying the renal responses seem different for the two types of expansion. It has been suggested that the response to saline expansion is due to changes in physical factors with alterations in the morphology of the lateral intercellular space (LIS). The present study examines the width of the LIS of the proximal tubule after a Ringer-Locke (1%, 2.3%, or 7% body weight) or whole blood (2.3% body weight) infusion and in nonexpanded control. After Ringer-Locke infusion, a significant widening of the LIS of the proximal tubule is seen at all levels of expansion. There is a linear relationship between the level of the Ringer-Locke infusion and the degree of expansion of the LIS. In contrast, after blood volume expansion, the width of the LIS is the same as nonexpanded controls. These studies are consistent with the view that the renal response to saline expansion is mediated at least in part by physical factors affecting the proximal tubule.