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Intermittent hypoxia in rats augments myogenic contraction in mesenteric arteries.
Author(s) -
JacksonWeaver Olan,
Bosc Laura Gonzales,
L Nancy
Publication year - 2008
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.22.1_supplement.1181.12
Subject(s) - mesenteric arteries , myogenic contraction , contraction (grammar) , endocrinology , medicine , chemistry , hypoxia (environmental) , vasoconstriction , vascular smooth muscle , anatomy , smooth muscle , artery , oxygen , organic chemistry
Myogenic tone is an important regulator of vascular resistance and is increased in several models of hypertension. Ca 2+ sparks can decrease vascular smooth muscle contraction and have been proposed to regulate myogenic tone. We previously reported that exposing rats to eucapnic intermittent hypoxia (E‐IH) to simulate sleep apnea causes hypertension and augments agonist‐induced vascular reactivity. We hypothesized that E‐IH increases myogenic reactivity and decreases Ca 2+ spark frequency in rat mesenteric arteries. Small mesenteric arteries were dissected from rats exposed to E‐IH or air cycling (Sham) for 14 days. Intracellular Ca 2+ concentration ([Ca 2+ ] i ) and inner diameter (i.d.) were recorded in pressurized arteries loaded with fura‐2 AM. Rapid intracellular Ca 2+ events were recorded in arteries loaded with fluo‐4 AM. Elevating intraluminal pressure from 60 to 100 mmHg increased myogenic tone and global [Ca 2+ ] i in arteries from E‐IH rats (13.20 ± 5.49 to 30.63 ± 5.56 % Ca 2+ ‐free i.d. and 1.33 ± 0.11 to 1.56 ± 0.11 F 340 /F 380 ) but not those from Sham rats (11.56 ± 2.95 to 13.97 ± 3.37 % Ca 2+ ‐free i.d. and 1.30 ± 0.07 to 1.44 ± 0.08 F 340 /F 380 ). The same pressure step tended to increase spark frequency in Sham but not E‐IH arteries. These results support our hypothesis that E‐IH augments the development of myogenic tone through increased global [Ca 2+ ] i associated with decreased Ca 2+ spark frequency.