Effects of the perfusion flow rate on skeletal muscle energy metabolism and a possible role of second messengers in this process.

The metabolic turnover in the isolated in vitro perfused and superfused rat skeletal muscle (musculus gracilis cranialis) was enhanced by increasing the medium flow rate under relaxed conditions. In a recent study we have measured the tissue concentrations of second messengers: cyclic adenosine 3'5'-monophosphate (cAMP), cyclic guanosine 3'5'-monophosphate (cGMP), and D-myo-inositol 1,4,5-trisphosphate (IP3) under similar experimental conditions to analyze their potential role in the described stimulation of metabolic rate by changes of perfusion flow rate. The tissue levels of the two second messengers' cAMP and cGMP were not significantly changed after increasing the perfusion flow rate and they probably have no transduction role in the induced alteration of skeletal muscle metabolism. However, the IP3 content was extremely reduced after increasing flow rate. This decrease in the tissue concentration of IP3 induced by increasing the flow rate indicates the possible role of IP3 in this signal transduction, leading to changes in the cellular metabolic pathways.