Effect of calcium on sulfated mucous glycoprotein secretion in dog trachea

In this experiment utilizing dog trachea we determined the effect of calcium concentration in the bathing media on the kinetics of secretion of sulfate incorporated into mucous glycoprotein. The results showed that in eight tracheas the secretion rate of 269 +/- 65 pmol SO4 . cm-2 . hr-1 (mean +/- SE) of tissues bathed in solution lacking calcium throughout the experiment was significantly less than the rate of 526 +/- 87 pmol SO4 . cm-2 . hr-1 of tissues bathed in solution containing 1.9 mM Ca2+. When tissues bathed in 1.9 mM CA2+ were incubated with 35SO4 to a constant secretion rate and then placed in 0 mM Ca2+ solution, the secretion of incorporated sulfate was unchanged relative to tissues bathed 1.9 mM Ca2+ throughout the experiment. Pool size of 727 +/- 150 pmol SO4/cm2 in tissues incubated in 0 mM Ca2+ throughout the experiment was significantly less than the pool size of 1,069 +/- 190 pmol SO4/cm2 in 1.9 mM Ca2+ solutions. This study showed that either the uptake of sulfate and/or biosynthetic pool size of sulfate incorporated into mucous glycoproteins was decreased in solution lacking calcium. However, release of sulfate incorporated into mucous glycoprotein in the lumen was independent of calcium in the external bathing media.