A LABILE SODIUM-PUMP INHIBITOR FROM THE PERITONEAL DIALYSATE OF HYPERTENSIVE RENAL-FAILURE PATIENTS - ESTIMATES OF POTENCY

Estimations of concentration of the labile sodium pump inhibitor isola ted from human peritoneal dialysate were made using supercritical flui d chromatography coupled to flame ionization detection to determine th e quantity of this factor in half of a purified preparation of the fac tor compared to the bioactivity of the other half in different assays. Ouabain was used for comparison. The labile factor appeared to be 30 times more effective than ouabain against canine renal [Na,K]ATPase. M oreover, this same factor appeared to be similar to 1,000 times more p otent than ouabain in causing vascular smooth muscle contraction. The differences between this labile sodium pump inhibitor and ouabain most likely reflect their respective binding affinities. The assay differe nces in half maximal response to the labile sodium pump inhibitor may be due to differences in sodium pump alpha isoform sensitivity.