Double knockout of connexins discloses myoendothelial cell communication in mouse cremasteric arterioles.

Abstract

We utilized homologous recombination to produce conditional endothelial cell-specific knockout of connexin 43 (EC KO), global knockout of connexin 40 (40 KO) and a combination of the two deletions (double KO) in mice. Reactivity to phenylephrine (PE), KCL, and acetylcholine (ACh) were assessed using micropipette application of the agents. Responses were compared at the site of application (local) and at 500 and 1000 mm distant. The response to PE in WT, Cx40 KO and EC KO animals consisted of a rapid arteriolar contraction that peaked within 4 sec and then returned to baseline over approximately 40 sec. In response to PE, arterioles in the double KO animal manifested an extended (recovery > 1 min) and larger local response, and a proportional increase in the magnitudes of the conducted vasomotor responses. Conducted responses at 500 and 1000 μm were similar, suggesting that the longitudinal communication pathway was relatively intact in spite of the manipulation of connexins 40 and 43. The arteriolar responses to PE in the double knockout animals are similar to responses previously reported when endothelial cell Ca++changes in response to PE were buffered using BAPTA (Yashiro and Duling, Circ. Res. 87:1048, 2000), and we therefore hypothesize that deletion of the two connexins eliminates some aspect of cell-cell communication. Supported by USPHS Grant # HL53318