Effects of manganese and other divalent cations on calcium uptake and catecholamine secretion by primary cultures of bovine adrenal medulla cells

Abstract Primary cultures of bovine adrenal medullary chromaffin cells were used to examine the effect of replacing divalent cations in the extracellular media on secretion. When calcium was replaced by manganese, nicotine-stimulated secretion was delayed in onset for 3 to 5 minutes, but continued for approximately 60 minutes. In contrast, calcium-supported secretion began immediately on stimulation and plateaued by 10 minutes. 54 Mn 2+ uptake occurred on stimulation but at a lower rate than 45 Ca 2+ uptake. There was no delay of 54 Mn 2+ uptake upon stimulation and 54 Mn 2+ uptake was considerably prolonged compared to 45 Ca 2+ uptake. Replacement of calcium with strontium gave results similar to those with calcium, and, in addition, strontium was able to bring about secretion by itself in a manner similar to barium. Inhibition experiments showed that the potency for inhibiting calcium uptake was Cd 2+ >Mn 2+ >Ca 2+ >Sr 2+ .