REGULATION BY PURINERGIC AGONISTS OF ZINC UPTAKE BY RAT SUBMANDIBULARGLANDS

The zinc uptake in rat submandibular cells was measured using fura2 as a fluorescent probe. Basal zinc uptake was observed in a 100 mu M - 1 mM concentration range. Carbachol and isoproterenol had no effect but ATP(4-) dose-dependently increased the basal zinc uptake (half-maxima l concentration: 250 mu M) The purinergic agonist shifted the concentr ation curve for zinc to the left by one order of magnitude. The respon se to ATP was not reproduced by adenosine or ADP and was blocked by Co omassie blue. Calcium, nickel or lanthanum were inhibitors of zinc upt ake, while the substitution of extracellular sodium by potassium or li thium increased the basal zinc uptake. We conclude that in submandibul ar cells zinc can permeate through the non-specific cation channel cou pled to ATP-sensitive purinergic receptors.