Cardiac glycosides are crucial drugs affecting heart muscle function.
Understanding cardiac glycoside binding is vital for therapeutic applications and disease monitoring.
Human blood cells offer a potential model for studying these binding dynamics.
Purpose of the Study:
To investigate 3H-ouabain binding to intact human mononuclear leucocytes.
To compare the binding characteristics with those of human heart muscle.
To assess the suitability of leucocytes as a model for physiological or disease-induced changes in cardiac glycoside binding.
Main Methods:
Incubation of leucocyte suspensions from normal subjects with 3H-ouabain.
Quantification of 3H-ouabain binding using radioligand assay.
Analysis of binding affinity (KD), association (k+1), and dissociation (k-1) rates.
Determination of the number of ouabain binding sites per leucocyte.
Main Results:
3H-ouabain exhibited specific binding to a single type of site on mononuclear leucocytes.
The affinity (KD) of binding was comparable to that observed in human heart muscle.
Binding association and dissociation rates were slow.
Significant inter- and intra-individual variations in the number of binding sites were observed.
Conclusions:
The ouabain binding site on human heart muscle is likely identical to that on intact mononuclear leucocytes.
Despite similar binding affinity, the substantial variability in binding site number within leucocyte mixtures limits their use for quantifying drug- or disease-induced changes.