Immunofluorescence detection of digoxin with monoclonal digoxin specific antibody.

The present study primarily focuses on the analysis of digoxin binding of the heart muscle cells. The primary aim of the investigation was to demonstrate the cardiac glycoside morphologically. The direct immunofluorescence staining technique with digoxin specific monoclonal antibody or Fab fragments and FITC or Texas-Red conjugated antisera are useful for morphological demonstration of digoxin binding and localization in cardiac cells. With the immunofluorescence method, linkage can be observed on the sarcolemma membrane and on the wall of capillaries and arterioles in myocardial cells treated by cardiac glycoside. The specificity of reaction is provided by the negative reaction of cells, not treated by digoxin. Intensity of reaction depends on concentration. The photometric measuring of fluorescence enables the quantitative analysis of cardiac glycoside. It shows the sensitivity of the method in that cardiac glycoside linked to the cell membrane can be detected in the upper sphere of a therapeutic dose. Application of the immunofluorescence method is manifold and relatively simple, and this quick method can be used in diagnoses and in the study of cardiac glycoside receptors of cell membrane. On the basis of our own experiments it is possible to study the kinetics of digoxin linkage. The use of this method is demonstrated for investigation of single cell suspension and cryostat sections.