CHARACTERIZATION OF A URINARY BUFODIENOLIDE NA-ATPASE INHIBITOR IN PATIENTS AFTER ACUTE MYOCARDIAL-INFARCTION(,K+)

Recent evidence suggests the existence of several endogenous Na+,K+-AT Pase inhibitors in mammals. Previously, we have shown that the amphibi an Na+,K+-ATPase inhibitor marinobufagenin (3,5-dihydroxy-14,15-epoxy bufodienolide) acts as a vasoconstrictor in isolated rat and human art eries. Mammalian plasma was shown to contain marinobufagenin-like immu noreactive material, which is responsive to saline volume expansion. T he present study describes purification of a bufodienolide, which is s imilar to marinobufagenin, from the urine of patients after acute myoc ardial infarction with the use of thin-layer chromatography and revers e-phase high-performance liquid chromatography (HPLC). The purified su bstance cross-reacted with marinobufagenin antibody, demonstrated maxi mal UV absorbance at 300 nm characteristic of bufodienolides, and elut ed from HPLC columns with the same retention time as marinobufagenin. Mass spectrometry of purified material revealed the presence of a subs tance indistinguishable from amphibian marinobufagenin and having mole cular mass of 400 D. The present studies show that one of the human di gitalis-like factors may have a bufodienolide structure and is likely to represent marinobufagenin or its isomer, and they suggest a role fo r this substance in the pathogenesis of myocardial ischemia.