Segment-specific differences in the inward rectifier K+ current along the renal interlobular artery

Chilton, Lisa, Smirnov, Sergey V., Loutzenhiser , Kathy, Wang, Xuemei, and Loutzenhiser, Rodger (2011) Segment-specific differences in the inward rectifier K+ current along the renal interlobular artery. Cardiovascular Research, 92 (1). pp. 169-177.

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DOI: 10.1093/cvr/cvr179

View at Publisher Website: http://dx.doi.org/10.1093/cvr/cvr179

Abstract

Aims: We investigated the role of the inward rectifier K+ channel (KIR) in the renal interlobular artery (ILA). The ILA supplies the afferent arteriole and ranges in diameter from >100 µm near its origin at the arcuate artery to <30 µm at its most distal segment.

Methods and results: Vasodilatory responses to elevated extracellular K+ (15 mmol/L) and vasoconstrictor responses due to KIR blockade by Ba2+ (10–100 µmol/L) were assessed in in vitro perfused hydronephrotic rat kidneys. The distal ILA (26 ± 1 µm) exhibited K+-induced dilation and Ba2+-induced vasoconstriction, whereas neither response was observed in the proximal ILA (108 ± 3 µm). The intermediate ILA (55 ± 1 µm) exhibited a modest K+-induced vasodilatation, but no Ba2+-induced vasoconstriction. The K+-induced dilations were blocked by Ba2+, but not by ouabain. Ba2+-induced depolarization, measured in ILA segments from normal kidneys, decreased with the increasing diameter. Patch-clamp studies demonstrated that the KIR current (IKIR) density also was inversely correlated with ILA segment diameter. Myocytes from afferent arterioles and distal ILAs exhibited similarly large IKIR, whereas this current was absent in proximal ILA myocytes. Finally, we found that Ba2+ attenuated myogenic vasoconstriction, suggesting an involvement of IKIR. The previously shown pattern of myogenic reactivity of the ILA (distal > intermediate > proximal) mirrors the distribution of IKIR reported in the present study, further supporting a role for IKIR.

Conclusion: Our findings indicate differences in the magnitude of IKIR along the ILA and suggest that the influence of KIR on reactivity increases as vessel diameter decreases from proximal to distal regions.


Item ID:	18561
Item Type:	Article (Research - C1)
ISSN:	1755-3245
Keywords:	renal microcirculation, smooth muscle cells, potassium channels, patch-clamp technique, interlobular artery
Funders:	Canadian Institutes for Health Research, Heart and Stroke Foundation of Alberta, Inuit and N.W.T., Alberta Heritage Foundation for Medical Research, The Killam Foundation
Projects and Grants:	MOP-14075, 20090234, 20091182
Date Deposited:	26 Mar 2012 04:21
FoR Codes:	06 BIOLOGICAL SCIENCES > 0606 Physiology > 060603 Animal Physiology Systems @ 80% 11 MEDICAL AND HEALTH SCIENCES > 1102 Cardiovascular Medicine and Haematology > 110201 Cardiology (incl Cardiovascular Diseases) @ 10% 11 MEDICAL AND HEALTH SCIENCES > 1116 Medical Physiology > 111603 Systems Physiology @ 10%
SEO Codes:	92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920119 Urogenital System and Disorders @ 50% 92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920103 Cardiovascular System and Diseases @ 50%
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