Quantification and preservation of lectin binding by isolated cardiomyocytes

During preparation of cells for experimentation a considerable amount of bound substance is lost. Our aim was to develop a protocol which retained lectin binding to an extent similar to living cells. This procedure would use fixation procedures suited for fluorescent lectin conjugates and gold-conjugates to be visualized by light- and electron microscopy, respectively. We tested glutaraldehyde and paraformaldehyde in different concentrations before and after lectin binding, different buffers and divalent cations, as additives, to determine the effects on preservation of lectin binding. Lectin binding was visualized and semiquantitatively evaluated by image analysis in the light microscope after silver enhancement of lectin-gold conjugates and by using tetramethyl rhodaminyl isothiocyanate (TRITC)-conjugated lectins. Preservation of lectin binding was best visualized with fluorescent lectin conjugates, whereas during silver enhancement procedures of gold-conjugated lectins, a considerable amount of bound lectins was lost. In general, lectin binding to living cells followed by fixation is superior to fixation before lectin binding. Unfavourable combinations of fixatives and buffers can cause a loss of more than 90% bound lectin. In our experiments with freshly isolated guinea pig cardiomyocytes, lectin binding was best when we used Na-cacodylate buffer with glutaraldehyde fixation (0.1%) after binding of lectins to the living cells.