Plasma marinobufagenin-like and ouabain-like immunoreactivity in adrenocorticotropin-treated rats.
Recently, an endogenous digitalis-like factor (EDLF) was shown to be stimulated in corticotropin (ACTH) hypertension in the rat. We have shown that mammalian plasma contains a vasoconstrictor Na,K-ATPase inhibitor, which cross-reacts with an antibody to amphibian EDLF, marinobufagenin. In the present experiment, the effect of 8 days of intramuscular ACTH treatment (0.5 mg/kg/day) of male Fisher 344 x NB rats on blood pressure, plasma ouabain-like and marinobufagenin-like immunoreactivity, and on the activity of Na,K-ATPase in aortic sarcolemma were studied. The ACTH treatment for 8 days resulted in increased systolic blood pressure (151 +/- 12.4 v 121 +/- 4.0 mm Hg, P < .01), inhibition of Na,K-ATPase in aortic sarcolemma (2.99 +/- 0.35 v 5.43 +/- 0.17 micromol ADP/mg(prot)/h), and increases in plasma concentration of marinobufagenin-like (0.44 +/- 0.06 v 0.21 +/- 0.05 nmol/L), but not ouabain-like (0.09 +/- 0.01 v 0.10 +/- 0.04 nmol/L) immunoreactivity. In dissociation enhanced lanthanide fluoroimmunoassay (DELFIA), serial dilutions of plasma from ACTH-treated rats extracted with 25% and 80% acetonitrile, respectively, demonstrated parallelism to the calibration curves of ouabain and marinobufagenin. These findings suggest that an endogenous bufodienolide Na,K-ATPase inhibitor, rather than an endogenous ouabain-like compound, is increased after 8 days of treatment of rats with ACTH.
Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, Maryland 21224, USA. fedorovo@grc.nia.nih.gov
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Fedorova
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Anderson
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Bagrov
D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002018:Bufanolides / Q000097:blood*; D004912:Erythrocytes / Q000187:drug effects / Q000201:enzymology; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000097:blood / Q000139:chemically induced; D007118:Immunoassay; D008297:Male; D010042:Ouabain / Q000097:blood*; D051381:Rats; D011916:Rats, Inbred F344; D012508:Sarcolemma / Q000187:drug effects / Q000201:enzymology; D012964:Sodium / Q000097:blood; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism; D013599:Systole
D002018:Bufanolides; C093896:marinobufagenin; D010042:Ouabain; D000324:Adrenocorticotropic Hormone; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase