Capacitative Ca2+ entry in enteric glia induced by thapsigargin and extracellular ATP

Abstract

Mobilization of intracellular Ca2+ stores is coupled to Ca2+ influx across the plasma membrane, a process termed capacitative Ca2+ entry. Capacitative Ca2+ entry was examined in cultured guinea pig enteric glia exposed to 100 μM ATP, an inositol trisphosphate-mediated Ca2+-mobilizing agonist, and to 1 μM thapsigargin, an inhibitor of microsomal Ca2+ ATPase. Both agents caused mobilization of intracellular Ca2+stores followed by influx of extracellular Ca2+. This capacitative Ca2+ influx was inhibited by Ni2+ (88 ± 1%) and by La3+ (87 ± 1%) but was not affected by L- or N-type Ca2+channel blockers. Pretreatment of glia with 100 nM phorbol 12-myristate 13-acetate for 24 h decreased capacitative Ca2+ entry by 48 ± 2%. Chelerythrine (0.1–10 μM), a specific antagonist of protein kinase C (PKC), dose dependently inhibited capacitative Ca2+ entry. The nitric oxide synthase inhibitor N G-nitro-l-arginine (1 mM) decreased Ca2+ influx by 42 ± 1%. Capacitative Ca2+ entry was inhibited to a similar degree by the guanylate cyclase inhibitor (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one). Capacitative Ca2+ entry occurs in enteric glial cells via lanthanum-inhibitable channels through a process regulated by PKC and nitric oxide.