Effects of ghrelin on the intracellular calcium concentration in rat aorta vascular smooth muscle cells.

BACKGROUND/AIMS Ghrelin has been regarded as a cardioprotective factor with complicated mechanisms. Whether ghrelin is vasodilative or vasoconstrictive in nature is controversial, and the effects of ghrelin on intracellular calcium concentration are still unclear. To explore the mechanisms involved in the vasoactive regulation of ghrelin at the cellular level, we investigated the effects of ghrelin on calcium concentrations in rat aorta vascular smooth muscle cells (VSMCs). METHODS We obtained VSMCs via cell culture and stained the cells with Furo-2 AM. Western blotting was used to verify growth hormone secretagogue receptor (GHS-R1a) expression in VSMCs. The intracellular calcium variations affected by ghrelin and the interactions of ghrelin with angiotensin II (AngII), Sq22536, and potassium chloride (KCl) were observed using a calcium imaging and analysis system. RESULTS Western blotting revealed good GHS-R1a expression in VSMCs. The most prominent finding in the present study was that ghrelin inhibited the AngII-induced increase in the calcium concentration. This inhibition was reversed by the adenylate cyclase inhibitor Sq22536 and the GHS-R1a antagonist (D-Lys(3))- GHRP-6. This finding revealed the potential vasodilative effects of ghrelin at the cellular level. We did not observe any effects of ghrelin on intracellular calcium concentrations in resting VSMCs or the increase of calcium concentration induced by KCl. CONCLUSION Ghrelin inhibited the increase in the intracellular calcium concentration of rat aorta VSMCs induced by AngII, which may depend on the activation of the cAMP/PKA pathway.