Fig. 7.

Roles of endothelial inward rectifier K⁺ (K_ir) channels in maintaining the synchrony of spontaneous Ca²⁺ transients.

Ba²⁺ (50 μM), a blocker of K_ir channels, converts synchronous spontaneous Ca²⁺ transients into asynchronous, high-frequency Ca²⁺ transients in the rat rectal precapillary arteriole (PCA) (A). Subsequent nifedipine does not recover the synchrony. Immunohistochemistry reveals that eNOS-positive endothelium of PCA in the rat rectum expresses K_ir2.1 (B–D). In a cross section of rat rectum, K_ir2.1 immunoreactivity is not colocalised with α-smooth muscle actin (α-SMA)-immunoreactive vascular smooth muscle cells (VSM) of submucosal blood vessels (E–G). MM indicates the muscularis mucosae. Traces and micrographs are reproduced from (49) with permission.