No abstract

We examined gap junction coupling of descending vasa recta (DVR). DVR endothelial cells or pericytes were depolarized to record the associated capacitance transients. Virtually all endothelia and some pericytes exhibited prolonged transients lasting 10 -30 ms. Carbenoxolone (100 M) and 18␤-glycyrrhetinic acid (18␤GRA; 100 M) markedly shortened the endothelial transients. Carbenoxolone and heptanol (2 mM) reduced the pericyte capacitance transients when they were prolonged. Lucifer yellow (LY; 2 mM) was dialyzed into the cytoplasm of endothelial cells and pericytes. LY spread diffusely along the endothelial monolayer, whereas in most pericytes, it was confined to a single cell. In some pericytes, complex patterns of LY spreading were observed. DVR cells were depolarized by voltage clamp as fluorescence of bis(1,3-dibarbituric acid)-trimethine oxanol [DiBAC4(3)] was monitored ϳ200 m away. A 40-mV endothelial depolarization was accompanied by a 26.1 Ϯ 5.5-mV change in DiBAC4(3) fluorescence. DiBAC4(3) fluorescence did not change after 18␤GRA or when pericytes were depolarized. Similarly, propagated cytoplasmic Ca 2ϩ responses arising from mechanical perturbation of the DVR wall were attenuated by 18␤GRA or heptanol. Connexin (Cx) immunostaining showed predominant linear Cx40 and Cx43 in endothelia, whereas Cx37 stained smooth muscle actinpositive pericytes. We conclude that the DVR endothelium is an electrical syncytium and that gap junction coupling in DVR pericytes exists but is less pronounced.