Effect of triiodothyronine on (Na+ G K+)-adenosine triphosphatase and (Na+ + Mg2+)-dependent phosphorylated intermediate in rat salivary glands.

The present studies concern the effect of triiodothyronine (T3) on rat salivary (Na+ + K+)-adenosine triphosphatase (NaK-ATPase). The results indicate that T3 selectively increased submandibular and parotid NaK-ATPase units with a single, large dose of T3, different dosage of T3, three successive doses of T3 given on alternate days, and "physiological" doses of T3 with daily injection for 2 weeks. Sublingual NaK-ATPase was insensitive to T3 in the above experiments. The effect of T3 on submandibular and parotid NaK-ATPase is selective since Mg-ATPase and 5'-nucleotidase showed no significant differences under different thyroid status. The lack of response of NaK-ATPase to reverse T3, further substantiates the specificity of T3 on salivary NaK-ATPase.