Caffeine, a methyl xanthine, has been added to a variety of cell types. Which one of the following would be expected in various cell types treated with caffeine and epinephrine?
If the phosphodiesterase that degrades cAMP were inhibited (an effect of caffeine) in the presence of epinephrine, cAMP levels would be elevated. PKA would become more active in the liver and muscle; pyruvate kinase would become less active in the liver; and glycogen synthase activity would be decreased in both the muscle and the liver. Phosphorylase activity would be increased in both the muscle and the liver owing to constant phosphorylation by phosphorylase kinase, which is activated by PKA.
Decreased activity of liver PKA
Decreased activity of muscle PKA
Increased activity of liver pyruvate kinase
Decreased activity of liver glycogen synthase
Carbohydrates