This abstract assesses electrical coupling between pericytes and other cells in descending vasa recta (DVR), by comparing the input resistances of pericytes on isolated DVR before and during exposure to 18β-glycyrrhetinic acid (βGA), a gap junction blocker (Hill et al. 2001). Other microvessels show intercellular coupling via gap junctions (made of connexins 37, 40 and 43) and this may modulate vasoactivity (Hill et al. 2001). DVR from rats are vasoactive (Pallone, 1994) and may regulate the distribution of blood flow to the renal medulla (Mattson, 2003), but vasa recta from mice lack immunoreactivity to connexin 40 (Seul & Beyer, 2000).

Input resistance was measured by whole cell perforated patch clamp recording. Individual DVR were dissected from renal tissue kept at 4 °C, after removal from rats (Pallone, 1994) humanely killed by stunning and cervical dislocation. DVR were incubated in collagenase and hyaluronidase (0.4 mg ml^-1 of each) at room temperature for 8-9 min, stored on ice and transferred at intervals to control solution at room temperature, containing (mM) Na⁺ 150, K⁺ 5, Mg²⁺ 1, Ca²⁺ 1, Cl^– 159, Hepes 10 and glucose 10, plus dimethylsulfoxide (0.1 %). Heat polished pipettes containing a solution of (mM) Na⁺ 10, K⁺ 140, Cl^– 150 and Hepes 10, plus gramicidin (0.4 mg ml^-1) and dimethylsulfoxide (0.4 %), were applied to pericytes on isolated DVR, to form gigaohm seals. Pericytes were clamped at -50 mV and exposed every 10 s to a series of steps from this holding potential to test potentials from -80 to +20 mV (at 10 mV intervals), each lasting 100 ms. Input resistance was calculated for each series, from the relationship between test potential -80 to -40 mV) and mean current between 95-99 ms during each step, by linear regression. βGA (40 µM) was added once to each of eleven DVR. Pericytes on isolated DVR displayed a significant increase in mean input resistance on exposure to βGA. The data indicate that pericytes can be electrically coupled to other cells in these DVR, perhaps via gap junctions.

This work was supported by British Heart Foundation grant PG/2000105.