Influence of infrasound exposure on the whole L-type calcium currents in rat ventricular myocytes.
This study was designed to examine the effect of infrasound exposure (5 Hz at 130 dB) on whole-cell L-type Ca2+ currents (WLCC) in rat ventricular myocytes and the underlying mechanism(s) involved. Thirty-two adult Sprague-Dawley rats were randomly assigned to infrasound exposure and control groups. [Ca2+](i), WLCC, mRNA expression of the a(1c) subunit of L-type Ca2+ channels (LCC), and SERCA2 protein were examined on day 1, 7, and 14 after initiation of infrasound exposure. Fluo-3/AM fluorescence and the laser scanning confocal microscope techniques were used to measure [Ca2+](i) in freshly isolated ventricular myocytes. The Ca2+ fluorescence intensity (FI), denoting [Ca2+](i) in cardiomyocytes, was significantly elevated in a time-dependent manner in the exposure groups. There was a significant increase in WLCC in the 1-day group and a further significant increase in the 7- and 14-day groups. LCC mRNA expression measured by RT-PCR revealed a significant rise in the 1-day group and a significant additional rise in the 7- and 14-day groups compared with control group. SERCA2 expression was significantly upregulated in the 1-day group followed by an overt decrease in the 7- and 14-day groups. Prolonged exposure of infrasound altered WLCC in rat cardiomyocytes by shifting the steady-state inactivation curves to the right (more depolarized direction) without altering the slope and biophysical properties of I (Ca,L). Taken together, our data suggest that changes in [Ca2+](I) levels as well as expression of LCC and SERCA2 may contribute to the infrasound exposure-elicited cardiac response.
Pei
Zhaohui
Z
Department of Pharmacology, Zhongshan Medical College, Sun Yat-Sen University, Guangzhou, Guangdong 510080, China.
Zhuang
Zhiqiang
Z
Xiao
Pingxi
P
Chen
Jingzao
J
Sang
Hanfei
H
Ren
Jun
J
Wu
Zhenbiao
Z
Yan
Guangmei
G
D000161:Acoustic Stimulation / Q000009:adverse effects* / Q000379:methods; D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D020746:Calcium Channels, L-Type / Q000502:physiology*; D008297:Male; D032383:Myocytes, Cardiac / Q000166:cytology / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D020746:Calcium Channels, L-Type