Elevation of cyclic guanosine 3',5'-monophosphate levels in dog thyroid slices caused by acetylcholine and sodium fluoride.

Cyclic guanosine 3’,5’-monophosphate (cyclic GMP) levels were determined in dog thyroid slices using the protein-binding method. [aH]Guanine incorporation into cyclic GMP was also determined by thin layer chromatography. Basal levels of cyclic GMP in dog thyroid slices were usually 10 to 30 pmoles per g wet tissue. These values were at least lo-fold lower than the cyclic adenosine 3’,5’-monophosphate (cyclic AMP) levels. Cyclic GMP levels were significantly increased by acetylcholine (5.5 X IO-’ M to 5.5 X 10W6 M) and NaF (10m2 M) after a 1-min incubation. Increases (5 to lofold) were observed after 5and 20-min incubations with acetylcholine (5.5 X 10m5 M) and after a 20-min incubation with Na.F (10e2 M). Neither thyroid-stimulating hormone (100 milhunits per ml) nor prostaglandin Ei (2.8 X 10e5 M) increased cyclic GMP levels during l-, 5-, and 20-min incubations. Acetylcholine and NaE also increased [aH]guanine incorporation into cyclic GMP. The effect of acetylcholine was inhibited by atropine (1.6 X lo-* M). Acetylcholine and NaF had little or no effect on cyclic AMP levels, while thyroidstimulating hormone and prostaglandin Ei markedly increased cyclic AMP concentrations. In liver slices of the rat, acetylcholine increased cyclic GMP levels 2-fold, but NaF had no effect. These results indicate that the levels of cyclic GMP and cyclic AMP in dog thyroid slices are regulated by separate hormonal and metabolic mechanisms.