Hormonal regulation of hepatic glycogenolysis in the toad, Xenopus laevis, is mediated by cyclic AMP and not Ca2+

Hormonal response of primary hepatocytes of the clawed toad, Xenopus laevis

“…To analyze the effects of hormones on glucose release from the liver of Amphibia, it is most successful to use preparations of primary culture of hepatocytes of the clawed toad. The results confirm those found by other authors (Janssen and Grigg, 1984, 1987) using slices or cubes of liver tissue of these animals, however, the experiments with hepatocytes had the advantage of relating the effects clearly to the type of parenchymal cells which are the main source of the released glucose and are the cells which mainly store glycogen in the liver. This preparation was perferred because a clear correlation with the protein content of the cells could be made for both the amount of glycogen and released glucose.…”

“…Hepatic glycogenolysis and release of glucose is stimulated in liver pieces of serveral Amphibia by adrenaline and nonapeptides, e. g. arginine-vasotocin (AVT). This has been shown for the axolotl, Ambystoma mexicanum (Janssens et al, 1983;, and for the clawed toad, Xenopus laevis (Janssens and Grigg, 1984;1987). In both species, the effect of adrenaline as well as AVT was mediated by cyclic AMP and independent of external Ca It has been suggested that the effects were not induced by a release of Ca ± from intracellular stores via inositol-1,4,5-tri-phosphates (Janssens et al, 1986).…”