Effects of tumor necrosis factor-alpha on calcium movement in rat ventricular myocytes.
OBJECTIVE
To study the effects of tumor necrosis factor-alpha (TNF-alpha) on calcium movement in rat ventricular myocytes.


METHODS
Intracellular free Ca2+ concentration was measured with calcium fluorescent probe Fluo-3/AM and laser confocal microscope. L-type calcium current (ICa,L) was recorded with the whole-cell configuration of the patch-clamp techniques.


RESULTS
At 2, 20 and 200 microg/L, TNF-alpha was found to increase intracellular free Ca2+ concentration in a dose-dependent manner illustrated by the increment of calcium fluorescence density with laser confocal microscope. Nicardipine 0.5 micromol/L slightly attenuated TNF-alpha-induced response. When the cardiac myocytes were exposed to caffeine (100 mmol/L) for 30 min, TNF-alpha failed to induce any change of intracellular free calcium. However, it was found that TNF-alpha inhibited I(Ca,L) in whole-cell patch-clamp experiments. At 2, 20, and 200 microg/L, TNF-alpha decreased peak I(Ca,L) by 3.9 % (-5.1 pA/pF+/-0.3 pA/pF vs -4.9 pA/pF+/-0.2 pA/pF, n=9, P>0.05), 15.7 % (-5.1 pA/pF+/-0.3 pA/pF vs -4.3 pA/pF+/-0.3 pA/pF, n=9, P<0.05) and 19.6 % (-5.1 pA/pF+/-0.3 pA/pF vs -4.1 pA/pF+/-0.4 pA/pF, n=9, P<0.01), respectively. It shifted the steady-state inactivation curve of I(Ca,L) to the left (V1/2 shifted from -28.7 mV+/-0.3 mV to -37.8 mV+/-1.4 mV, n=7, P<0.05), while it took no effects on steady-state activation and recovery from inactivation.


CONCLUSIONS
TNF-alpha inhibited I(Ca,L) in rat ventricular myocytes, while increasing the intercellular free Ca2+ level due to the release of Ca2+ from intracellular stores.
Li
Xiao-Qiang
XQ
Department of Pharmacology, The Fourth Military Medical University, Xi-an 710032, China.
Zhao
Ming-Gao
MG
Mei
Qi-Bing
QB
Zhang
Yan-Feng
YF
Guo
Wei
W
Wang
Hai-Fang
HF
Chen
Dan
D
Cui
Yi
Y
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002469:Cell Separation; D006352:Heart Ventricles / Q000166:cytology; D008297:Male; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D020746:Calcium Channels, L-Type; D014409:Tumor Necrosis Factor-alpha; D002118:Calcium