IMMUNOREACTIVE ENDOGENOUS DIGOXIN-LIKE SUBSTANCES - PLASMA-LEVELS AREDEPENDENT ON THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS FOR RELEASE AND ON KIDNEY-FUNCTION FOR ELIMINATION

To identify factors that regulate the levels of immunoreactive digital is-like substances (irEDLS) in body fluids, two studies were carried o ut. Plasma and urine levels of irEDLS were measured in uremic and norm al subjects. Extracted material was fractionated (12 fractions) and as sayed by digoxin radioimmunoassay. In four fractions, higher levels of irEDLS were found in uremic than in normal plasma. Urine from healthy subjects contained very high levels of irEDLS, but in urine collected from uremic patients irEDLS levels were similar to those in plasma. I n another study, eight healthy subjects were given dexamethasone 1 mg orally and tetracosactide [an adrenocorticotropic hormone (ACTH) analo gue] 0.25 mg i.v., on separate occasions. Dexamethasone suppressed the plasma and urine levels of cortisol and irEDLS. ACTH increased the le vels of cortisol in plasma and urine, and of irEDLS in plasma. Taken t ogether, these results support the hypothesis that irEDLS are of adren al origin. However, decreased renal clearance, rather than increased p roduction or release, may be the main cause of increased plasma levels of irEDLS in uremia.