Potassium administration and calcitonin mRNA level in the rat.

We have investigated the acute effects of elevated plasma potassium concentrations on the calcitonin (CT) mRNA level measured by dot-blot hybridization. Plasma CT levels were significantly increased (X2) 30 min after potassium administration (1.2 mmol, KCl/100 g body weight) in adult female rats; a trend towards increased values was observed 10 min after treatment. No change in plasma calcium concentration was induced by the elevated extracellular potassium levels. The amount of CT mRNA measured by dot-blot hybridization was statistically significantly increased 10 min and 30 min (around 47-55%) after potassium treatment. This finding was confirmed by a Northern blot analysis. It is suggested for the first time that the potassium-induced CT release is associated with a slight increase in CT mRNA level. The increased CT secretion was probably mediated through a rise in the ionized calcium concentration of the C-cell.