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Effects of perfusion pressure on Ca 2+ sparks in rat renal afferent arterioles
Author(s) -
Balasubramanian Lavanya,
Sham J.S.K.,
Yip K.P.
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.761.21
Subject(s) - afferent arterioles , depolarization , myogenic contraction , chemistry , constriction , perfusion , arteriole , vascular smooth muscle , electrophysiology , medicine , biophysics , kidney , afferent , endocrinology , microcirculation , anatomy , blood pressure , smooth muscle , biology , angiotensin ii
Mechanical force can be transduced into freshly isolated renal vascular smooth muscle cells (VSMCs) to trigger Ca 2+ sparks. Sparks can trigger Spontaneous Transient Inward Currents (STICs), and regulate myogenic tone via membrane depolarization. Electrophysiological studies indicate the presence of STICs in isolated renal VSMCs. Hence, we sought to determine whether the occurrence of Ca 2+ sparks is increased during pressure induced myogenic constriction. Line scan images were collected from perfused rat afferent arterioles at 500 Hz using laser scanning confocal microscopy. We detected spontaneous Ca 2+ sparks in 40% of the VSMCs at a perfusion pressure of 80 mm Hg. These sparks were suppressed by 50 μM ryanodine and were augmented by 0.5 mM caffeine. The mean spontaneous Ca 2+ spark frequencies were 0.14±0.04 sparks/s (n=23 cells) and 0.24±0.11 sparks/s (n=13 cells) at 80 mm Hg and 120 mm Hg, respectively. These suggest that the increase in frequency of sparks is probably related to pressure induced myogenic constriction. Intriguingly, the frequency of Ca 2+ sparks observed in SHR afferent arteriole was double compared to that of normotensive rats at the same perfusion pressure. These observations implicate that the enhanced Ca 2+ sparks frequency may contribute to the increase of renal vascular resistance in SHR.