High K+ exposure has been shown to activate phosphoinositide turnover in skeletal muscle. To clarify the mechanism of this activation, we have studied the effect of caffeine on the metabolism of inositol phospholipids using [3H]myo-inositol labeled skeletal muscle of the frog. Caffeine significantly changed the phosphoinositide metabolism in a dose- and time-dependent manner. Being different from that of high K+, the effect of caffeine was characterized by an increase of the labeled phosphatidylinositol 4,5-bisphosphate (PIP2) and a decrease of the labeled inositol bisphosphate (IP2). In addition, high K+ supplemented during caffeine treatment caused an increase of the labeled inositol phosphates and a decrease of the labeled phosphatidylinositol 4-phosphate (PIP) and PIP2. It is suggested that the myoplasmic Ca2+ increase produced by high K+ exposure is not a sole factor for the activation of phosphoinositide metabolism, and the high K+-induced depolarization also plays a role.
|Original language||English (US)|
|Number of pages||6|
|Journal||Chinese Journal of Physiological Sciences|
|State||Published - Dec 1 1996|
- excitation-contraction coupling
- skeletal muscle
ASJC Scopus subject areas