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K channel contributions to afferent arteriolar tone in normal and diabetic rat kidney
Author(s) -
Brindeiro Carmen M. Troncoso,
Fallet Rachel W.,
Carmines Pamela K.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a501-b
Subject(s) - apamin , afferent arterioles , afferent , efferent , medicine , endocrinology , streptozotocin , chemistry , diabetes mellitus , anatomy , potassium channel , blood pressure , angiotensin ii
We previously reported ( JASN 11 : , 2000) an enhanced tonic dilator impact of ATP‐sensitive K + channels on afferent arterioles in rats with streptozotocin (STZ)‐induced diabetes. The present study explored the hypothesis that other types of K + channel also contribute to afferent arteriolar dilation in STZ rats. The in vitro blood‐perfused juxtamedullary nephron technique was utilized to quantify afferent arteriolar lumen diameter responses to K + channel blockers: 3 mM 4‐AP (K V channels), 30μM Ba 2+ (K IR channels), 100 nM Tertiapin‐Q (TPQ; Kir1.x & Kir3.x families of K IR channels), 100 nM apamin (SK Ca channels), and 1 mM TEA (BK Ca channels). In kidneys from normal rats, 4‐AP and TEA reduced afferent diameter by 23±4% and 8±4%, respectively (both P <0.05 vs baseline). Neither Ba 2+ , TPQ nor apamin significantly altered afferent diameter. A constrictor response to TPQ (16±7% decrease in diameter) emerged in arterioles from STZ rats, while responses to the other K + channel blockers were similar to those observed in normal rats. Moreover, TPQ reversed the afferent arteriolar dilation characteristic of STZ rats (Normal 19.3±0.9 μm, STZ 22.6±1.0 μm, P <0.05; Normal+TPQ 18.8±1.0 μm, STZ+TPQ 18.9±1.9 μm). We conclude that 1) K V and BK Ca channels tonically influence normal afferent arteriolar tone, and 2) Kir1.x and/or Kir3.x families of K IR channels contribute to the afferent arteriolar dilation during diabetes.