Effects of cyclic nucleotide derivatives on the Na+ pump activity and the release of sialic acid in dog submandibular glands.

The effects of dibutyryl cyclic AMP (DBcAMP) and cyclic GMP (DBcGMP) on the Na+,K+-ATPase activity and the release of sialic acid were investigated in dog submandibular gland pieces. The Na+,K+-ATPase activity and the release of sialic acid were significantly stimulated in the presence of 100 microM DBcAMP or in the combination of 3 mM NaF and 50 microM 1-methyl-3-isobutylxanthin but were not by DBcGMP. When the pieces were incubated in the Ca2+-free medium, the DBcAMP-induced Na+,K+-ATPase activity slightly decreased but the sialic acid release was unaffected. The corresponding results were also observed in the Ca2+-free medium supplemented with 2 mM EGTA. These results suggest that the cytosolic cyclic AMP modifies the Na+ pump activity.