Effect of hydrogen ions on influx and efflux of Ba2+ and Cd2+ in adrenal medulla.

To examine the possibility that enhanced uptake of Ba2+ and Cd2+ might explain the increased secretion induced by these metals at high pH, Ba2+ and Cd2+ were perfused through isolated bovine adrenals at high pH 7.4 and 8.3. Both metals were found in greater concentrations in the tissue after exposure at the high pH. Continued perfusion of adrenals with Locke's solution at pH 7.4 or 8.3 after exposure to the metals showed that Cd remaining in the tissue was not affected by the pH of the washout but residual Ba was greater after washout at the high pH. Catecholamine release was correlated with tissue Ba content regardless of the pH of the washout, but residual Cd was not correlated with amine secretion. It appears that low H+ concentrations increase influx of Ba2+ and Cd2+ into adrenomedullary cells and decrease efflux of Ba from this tissue. Elevated intracellular levels of Ba and Cd probably mediate the enhanced adrenomedullary secretion noted after exposure to the metals at high pH. Barium in the tissue is proportional to secretion, but it appears that only part of the Cd2+ entering the cells is involved in initiating adrenal catecholamine release.