Lysophosphatidylcholine (LPC) is an endogenous
phospholipid released from the cell membrane during
ischemia, and it has potent, local effects on cardiac tissues. LPC has been implicated in arrhythmogenesis during
ischemia by increasing intracellular Ca2+. However, it is not known whether LPC influences atrial release of
atrial natriuretic peptide (
ANP). The aim of this study was to investigate the effect of LPC on
ANP secretion from isolated, perfused, beating rat atria. LPC (10 and 30 micromol/L) caused decreases in
ANP secretion in a dose-dependent manner, with slight increases in intra-atrial pressure and extracellular fluid (ECF) translocation. Therefore, the
ANP secretion in terms of ECF translocation was markedly decreased by LPC. The order of the suppressive effect of
ANP release was stearoyl-LPC>LPC>myristoyl-LPC=lauroyl-LPC.
Staurosporine and
wortmannin significantly attenuated suppression of the
ANP release and an increase in intra-atrial pressure by LPC. High extracellular Mg2+ also attenuated the LPC-induced suppression of
ANP release. However, other
protein kinase C inhibitors such as
chelerythrine,
GF 109203X, and
tamoxifen citrate did not affect LPC-induced suppression of
ANP release. In single atrial myocytes, LPC caused increases in intracellular Ca2+ in a dose-dependent manner. The order of an increase in intracellular Ca2+ by LPC was stearoyl-LPC>LPC>myristoyl-LPC=lauroyl-LPC. An increase in intracellular Ca2+ by LPC was attenuated by
staurosporine. These results suggest that LPC-induced suppression of
ANP release through
protein kinase C/Ca2+ and phosphoinositol-3-kinase might in part play an important role in the development of
hypertension.