Involvement of PKA in lactic-acid-induced ATP release from cultured myocytes or perfused muscle.

Abstract

<p>A: PKA activity was measured in the supernatant from the L6 myocyte lysate following 30 mins incubation of the cells with the concentrations of lactic acid shown. The upper sample gel shows the separated bands of phosphorylated and non-phosphorylated peptide, and the lower gel shows the internal standard, β-actin, which was measured to confirm that the loading of the gel was kept constant. B: Appearance of ATP in the bathing medium of L6 myocytes exposed to 10 mM lactic acid in the absence or presence of KT5720 for 3 hrs. Values are the mean ± SEM of 9–13 tests. *, significant difference between the absence or presence of lactic acid; #, significant difference between the absence or presence of KT5720 (1-way ANOVA followed by the Bonferroni post-hoc t-test). C & D: Appearance of ATP in the interstitial space of buffer-perfused rat soleus muscle during infusion of lactic acid (5 mM) in the absence (C) or presence (D) of KT5720. Values are the mean ± SEM of 11 (C) or 6 (D) tests. *, significant difference between the absence or presence of lactic acid in 1-way repeated measures ANOVA followed by the Bonferroni post-hoc t-test.</p