Third factor and edema formation.

Urine extracts as well as plasma and urine fractions from normal persons during extracellular volume expansion and from patients with edema of different origin were tested for natriuretic (rat bioassay) and antinatriferetic (frog skin) activity. Whereas the extracts and fractions from normal persons with extracellular volume expansion proved to have a distinct natriuretic and antinatriferetic effect, no such effect was observed with urine and plasma preparations from patients with sodium retention and edema. Whether or not edema formation is mediated by a loss of natriuretic activity remains still to be clarified.