Figure 4.

Type 3 inositol-1,4,5-trisphosphate receptor 3 InsP₃R3 and two-pore channels 1 and 2 (TPC1-2) mediate endogenous Ca²⁺ release in response to arachidonic acid in hCMEC/D3 cells. (A) Endogenous Ca²⁺ mobilization induced by AA (30 μM) under 0Ca²⁺ conditions. (B) 2-aminoethoxydiphenyl borate (2-APB; 50 μM, 30 min) prevents AA-evoked endogenous Ca²⁺ release. In this and in the following panels, AA has always been applied at 30 μM. (C) Cyclopiazonic acid (CPA; 10 μM) inhibited Sarco-Endoplasmic Reticulum Ca²⁺-ATPase (SERCA) activity, thereby eliciting a transient elevation in [Ca²⁺]_i followed by Ca²⁺ removal from the cytosol. The following addition of AA did not result in an increase in [Ca²⁺]_i. (D) Glycyl-L-phenylalanine 2-naphthylamide (GPN; 200 μM) elicited a transient elevation in [Ca²⁺]_i due to the disruption of the lysosomal Ca²⁺ pool and the following liberation of lysosomal Ca²⁺ content into the cytosol [41,42]. The following addition of AA did not result in an increase in [Ca²⁺]_i. (E) NED-19) (100 μM, 30 min) blocked AA-evoked intracellular Ca²⁺ release. (F) Mean ± SE of the amplitude of the intracellular Ca²⁺ response to AA under the designated treatments. The asterisk indicates p < 0.05.