Regulatory effect of calcium on 3H-dopamine binding to guinea-pig heart membrane preparations.

The effects of various cations on the specific binding of dopamine to its recognition sites are described using guinea-pig heart membranes as a substrate. Only CaCl2 provoked a dose-dependent facilitatory effect, while KCl, NaCl and MgCl2 acted in the opposite sense. Moreover, Na2EDTA also had an inhibitory effect on dopamine binding and completely prevented the facilitatory action of CaCl2 on 3H-dopamine binding. This effect is partially counteracted by trifluoperazine but unaffected by verapamil. We can conclude from this that calcium seems to be essential to optimizing 3H-dopamine binding to cardiac membrane preparations.