Increased digitalis-like immunoreactive substances in patients with hypertrophic cardiomyopathy.
OBJECTIVE
Although increased digitalis-like immunoreactive substances have been found in cases of hypertension and heart failure, no information is available about digitalis-like immunoreactive substances in patients with hypertrophic cardiomyopathy. We investigated digitalis-like immunoreactive substances in the plasma and biopsied specimens of patients with hypertrophic cardiomyopathy.


RESULTS
In 40 patients with hypertrophic cardiomyopathy (27 with the non-obstructive type and 13 with the obstructive type), the plasma concentration of digitalis-like immunoreactive substances was studied by fluorescence polarization immunoassay. Right ventricular endomyocardial biopsy specimens were analysed immunohistochemically, using a monoclonal antibody against digoxin. An increase in digitalis-like immunoreactive substances of more than 0.2 ng. ml(-1)in plasma was found in six of 27 patients with non-obstructive hypertrophic cardiomyopathy (22.2%) and five of 13 with obstructive hypertrophic cardiomyopathy (38.4%). Under light microscopy, positive staining against the antibody was observed heterogeneously on some cardiocytes. In non-obstructive hypertrophic cardiomyopathy, digitalis-like immunoreactive substances in the plasma correlated with the left atrial dimension and inversely with the cardiac index. In obstructive hypertrophic cardiomyopathy, plasma and myocardial digitalis-like immunoreactive substances were positively correlated; they also correlated with left ventricular end-diastolic pressures. Under electron microscopy, digitalis-like immunoreactive substances were detected at the sarcolemma in the free wall, T-tubules, intercalated discs and Z-bands of cardiocytes.


CONCLUSIONS
Increased digitalis-like immunoreactive substances in plasma and cardiocytes, which may have been caused by pressure and/or volume overload, were found in patients with hypertrophic cardiomyopathy. Digitalis-like immunoreactive substances may act on the sarcolemma of cardiocytes and be transported into the cytoplasm.
Hayashi
T
T
The Third Division, Department of Medicine, Osaka Medical College, Takatsuki, Osaka, Japan.
Ijiri
Y
Y
Toko
H
H
Shimomura
H
H
Okabe
M
M
Terasaki
F
F
Kitaura
Y
Y
Kawamura
K
K
D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal; D002298:Cardenolides; D002312:Cardiomyopathy, Hypertrophic / Q000097:blood* / Q000503:physiopathology; D004077:Digoxin; D005260:Female; D016231:Fluorescence Polarization Immunoassay; D006439:Hemodynamics; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D012503:Saponins / Q000097:blood*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*
D000911:Antibodies, Monoclonal; D002298:Cardenolides; D012503:Saponins; C034504:digoxin-like factors; D004077:Digoxin; D000254:Sodium-Potassium-Exchanging ATPase