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NEUROHUMORAL CONTROL OF CARDIOVASCULAR FUNCTION

Descending vasa recta endothelium is an electrical syncytium

¹Division of Nephrology, Department of Medicine, and ²Department of Physiology, University of Maryland School of Medicine, Baltimore; and ³Department of Biology, Towson University, Towson, Maryland

Submitted 17 April 2006 ; accepted in final form 7 July 2006

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 µM) and 18-glycyrrhetinic acid (18GRA; 100 µM) 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 200 µm away. A 40-mV endothelial depolarization was accompanied by a 26.1 ± 5.5-mV change in DiBAC₄(3) fluorescence. DiBAC₄(3) fluorescence did not change after 18GRA or when pericytes were depolarized. Similarly, propagated cytoplasmic Ca²⁺ responses arising from mechanical perturbation of the DVR wall were attenuated by 18GRA or heptanol. Connexin (Cx) immunostaining showed predominant linear Cx40 and Cx43 in endothelia, whereas Cx37 stained smooth muscle actin-positive pericytes. We conclude that the DVR endothelium is an electrical syncytium and that gap junction coupling in DVR pericytes exists but is less pronounced.

rat; kidney; medulla; microcirculation; electrophysiology; blood flow

This article has been cited by other articles:

				Q. Zhang, C. Cao, Z. Zhang, W. G. Wier, A. Edwards, and T. L. Pallone Membrane current oscillations in descending vasa recta pericytes Am J Physiol Renal Physiol, March 1, 2008; 294(3): F656 - F666. [Abstract] [Full Text] [PDF]

				C. Cao, W. Lee-Kwon, K. Payne, A. Edwards, and T. L. Pallone Descending vasa recta endothelia express inward rectifier potassium channels Am J Physiol Renal Physiol, October 1, 2007; 293(4): F1248 - F1255. [Abstract] [Full Text] [PDF]