Identification of digitalis-like compounds in human cataractous lenses.
Human cataractous lens nuclei extract inhibited, in a dose-dependent fashion, [3H]ouabain binding to rat brain synaptosomes and microsomal Na(+)- and K(+)-dependent adenosine triphosphate (Na+, K(+)-ATPase) activity and interacted with anti-digoxin antibodies. The compounds responsible for these activities, termed digitalis-like compounds (DLC), were also detected in bovine, rat, cat and rabbit, normal, transparent lenses, but the levels were only 0.7-5.4% of the average levels in the cataractous human lenses. DLC from the human cataractous lenses were purified by a procedure consisting of organic extractions and batch chromatography followed by filtration through a 3000 Da cut-off filter and subsequent separations using reverse-phase high-performance liquid chromatography. The presence of DLC in the different fractions obtained in the chromatograms was monitored by their ability to inhibit [3H]ouabain binding and Na+, K(+)-ATPase activity. Based on chemical ionization mass spectrometry together with ultraviolet spectrometry and biological characterization, it is suggested that new bufodienolides, 19-norbufalin and 19-norbufalin peptide derivatives are responsible for the endogenous DLC activity. It is proposed that these compounds may regulate Na+, K(+)-ATPase activity in the lens under some physiological and pathological conditions.
Lichtstein
D
D
Department of Physiology, Hebrew University, Hadassah Medical School, Jerusalem, Israel.
Gati
I
I
Samuelov
S
S
Berson
D
D
Rozenman
Y
Y
Landau
L
L
Deutsch
J
J
D000818:Animals; D000906:Antibodies / Q000032:analysis; D001798:Blood Proteins / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D002018:Bufanolides / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D002298:Cardenolides; D002386:Cataract / Q000378:metabolism*; D004070:Digitalis / Q000378:metabolism*; D004077:Digoxin / Q000276:immunology; D006801:Humans; D007907:Lens Nucleus, Crystalline / Q000737:chemistry*; D013058:Mass Spectrometry; D008861:Microsomes / Q000378:metabolism; D008970:Molecular Weight; D010042:Ouabain / Q000378:metabolism; D010946:Plants, Medicinal; D010947:Plants, Toxic; D051381:Rats; D012503:Saponins; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*
D000906:Antibodies; D001798:Blood Proteins; D002018:Bufanolides; D002298:Cardenolides; D012503:Saponins; C034504:digoxin-like factors; D010042:Ouabain; D004077:Digoxin; D000254:Sodium-Potassium-Exchanging ATPase