Lipolysis and cyclic AMP response to isoproterenol in diaphragms from control and dystrophic mice

A comparison was made of the sensitivity of lipolysis (glycerol and free fatty acid release) and of cyclic AMP production to the action of isoproterenol in diaphragms from control and dystrophic Bar Harbor mice at 7 weeks of age. An increased lipolytic response was observed in diaphragms from dystrophic mice that was more apparent in the males, and was demonstrable when cyclic AMP was used instead of isoproterenol. The increased glycerol and free fatty acid release in response to isoproterenol and cyclic AMP cannot be explained by a higher triglyceride content of diaphragms from dystrophic mice, because it was found to be similar to that of controls when it was estimated by biochemical and light microscopic techniques. The increased lipolytic response was not paralleled by changes in cyclic AMP levels, which were found to be similar in diaphragms from control and dystrophic mice, whether in the basal or the stimulated state. It was concluded that the lipolytic apparatus in muscles from dystrophic mice shows an increased sensitivity to isoproterenol that seems to be related to events more intracellular than the cAMP production step.