Fig. 6. Selective knockdown of the Ins(1,4,5)P₃-R1 isoform eliminates the Ins(1,4,5)P₃ response in ECs. In the cartoons on the left, the pipette indicates the stimulated cell type (EC top, VSMC bottom), blue is BAPTA and `+' indicates the cell type that is loaded with siRNA. (A) When Ins(1,4,5)P₃-R1 was selectively deleted from the ECs, stimulation of BAPTA-loaded VSMCs no longer elicited an increase in EC [Ca²⁺]_i. (B) Knockdown of Ins(1,4,5)P₃-R2 and Ins(1,4,5)P₃-R3 using siRNA is demonstrated by the immunoblot, with β-actin loading controls shown directly underneath. (C,D) When Ins(1,4,5)P₃-R2 was knocked down, a polarized increase in EC [Ca²⁺]_i was still present (C), and the deletion of Ins(1,4,5)P₃-R3 also failed to inhibit increases in EC [Ca²⁺]_i (D). ^*P<0.05.