ENDOGENOUS NATRIURETIC FACTORS-2 - CHARACTERIZATION OF NATRIURETIC AND VASOPRESSIVE SUBSTANCES FROM HUMAN UREMIC URINE

It is our intention to isolate, purify, and characterize the putative low-molecular-weight ''natriuretic hormone'' responsible for extracell ular fluid (ECF) homeostasis. Toward this end, we are purifying from h uman uremic urine, and identifying endogenous vasopressor and natriure tic compounds. Bioactive components from large volumes of pooled urine were purified by ultrafiltration (less-than-or-equal-to 3 kDa), gel f iltration chromatography, and sequential reverse-phase and normal-phas e high-performance liquid chromatography (HPLC). After each HPLC step, the fractions were evaluated in vivo, were assayed for inhibition of Na+/K+-ATPase-mediated Rb-86+ uptake, and were checked for cross-react ivity with an anti-ouabain antibody. Fractions assayed in vivo were id entified that induced natriuresis, altered mean arterial pressure, or increased plasma cyclic-GMP. Also, many fractions inhibited Na+/K+-ATP ase and/or cross-reacted with anti-ouabain antibody. None of the in vi tro assays correlates with natriuretic or pressor effects. This pletho ra of bioactivities, revealed only with increased sample purity, may a ccount for much of the confusion and multiplicity of crude isolates cl aimed to be the putative hormone. Presently we are attempting to purif y and identify these natriuretic materials. One of these, a 3-substitu ted indole, has been partially characterized.