Role of intracellular cAMP in stimulating the increase in extracellular ATP at low pH.

Abstract

<p>A: influence of forskolin (20 µM) on the interstitial ATP of buffer-perfused rat soleus muscle. Values are the mean ± SEM of 5 observations. *, significantly greater than the precontrol in 1-way repeated measures ANOVA followed by the Bonferroni post-hoc t-test. B: comparison of the effect of forskolin (20 µM) or lactic acid (10 mM) in the absence or presence of IBMX on the appearance of ATP in the bathing medium of L6 cultured myocytes. Values are the mean ± SEM of 12–27 tests. *, significantly different from its own control group in Student's t-test; #, significant difference between the absence or presence of IBMX (Student's t-test). C: influence of lactic acid or sodium lactate on the intracellular cAMP of L6 cultured myocytes. Values are the mean ± SEM of 15 values for control and of 6–9 values for treatments. *, significantly different from control in 1-way ANOVA followed by the Bonferroni post-hoc t-test. D: determination of the maximal cAMP response to forskolin in the L6 myocytes: the line shows the 5-parameter sigmoid curve fit (r = 1.0) which predicts a maximal cAMP response of 9.0 nM.</p