Plasma marinobufagenin-like and ouabain-like immunoreactivity during saline volume expansion in anesthetized dogs.
OBJECTIVE
This study investigated effects of acute plasma volume expansion on plasma levels and urinary output of two endogenous Na,K-ATPase inhibitors, marinobufagenin-like and ouabain-like immunoreactive substances.


METHODS
Plasma volume was expanded for 3 h via intravenous saline infusion in three groups of anesthetized dogs--nontreated (n = 5); pretreated with rabbit antidigoxin (n = 5); and pretreated with rabbit antimouse (control) antibody (n = 4).


RESULTS
Plasma marinobufagenin-like immunoreactivity increased to 11.87 +/- 3.16 nmol.l-1 (vs. 0.30 +/- 0.16 nmol.l-1) within 10 min of volume expansion, in parallel with a 15% increase in LVdP/dt, then decreased to 2.21 +/- 0.59 nmol.l-1, and in 90 min increased to 11.8 +/- 2.8 nmol.l-1, in parallel with the maximal natriuretic response. Plasma concentrations of ouabain-like immunoreactive material were increased after 90 min of saline infusion (0.019 +/- 0.004 nmol.l-1 vs. 0.139 +/- 0.056 nmol.l-1). Pretreatment of the animals with antidigoxin antibody blocked the positive inotropic and reduced natriuretic response to volume expansion, and decreased the urinary release of marinobufagenin-like, but not ouabain-like, material.


CONCLUSIONS
These results show the presence of marinobufagenin-like immunoreactive substance in dog plasma and suggest that mammalian EDLF may have a bufodienolide nature. Endogenous marinobufagenin-like immunoreactive substance, which is likely to cross-react with antidigoxin antibody, is involved in the natriuretic and positive inotropic responses to plasma volume expansion.
Bagrov
A Y
AY
Laboratory of Behavioral Sciences, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA.
Fedorova
O V
OV
Dmitrieva
R I
RI
French
A W
AW
Anderson
D E
DE
D000818:Animals; D001323:Autoantibodies / Q000008:administration & dosage; D002018:Bufanolides / Q000097:blood* / Q000737:chemistry / Q000652:urine; D002024:Bufo marinus; D002298:Cardenolides; D004077:Digoxin / Q000276:immunology; D004285:Dogs; D018495:Fluid Shifts; D007106:Immune Sera; D008297:Male; D010042:Ouabain / Q000097:blood* / Q000737:chemistry / Q000652:urine; D010953:Plasma Volume; D012503:Saponins / Q000737:chemistry / Q000276:immunology; D012965:Sodium Chloride / Q000008:administration & dosage; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*
D001323:Autoantibodies; D002018:Bufanolides; D002298:Cardenolides; D007106:Immune Sera; D012503:Saponins; C034504:digoxin-like factors; C093896:marinobufagenin; D012965:Sodium Chloride; D010042:Ouabain; D004077:Digoxin; D000254:Sodium-Potassium-Exchanging ATPase