Influence of interleukin-2 on Ca2+ handling in rat ventricular myocytes.
In the present study, we examined the effect of interleukin-2 (IL-2) on cardiomyocyte Ca(2+) handling. The effects of steady-state and transient changes in stimulation frequency on the intracellular Ca(2+) transient were investigated in isolated ventricular myocytes by spectrofluorometry. In the steady state (0.2 Hz) IL-2 (200 U/ml) decreased the amplitude of Ca(2+) transients induced by electrical stimulation and caffeine. At 1.25 mM extracellular Ca(2+) concentration ([Ca(2+)](o)), when the stimulation frequency increased from 0.2 to 1.0 Hz, diastolic Ca(2+) level and peak intracellular Ca(2+) concentration ([Ca(2+)](i)), as well as the amplitude of the transient, increased. The positive frequency relationships of the peak and amplitude of [Ca(2+)](i) transients were blunted in the IL-2-treated myocytes. The effect of IL-2 on the electrically induced [Ca(2+)](i) transient was not normalized by increasing [Ca(2+)](o) to 2.5 mM. IL-2 inhibited the frequency relationship of caffeine-induced Ca(2+) release. Blockade of sarcoplasmic reticulum (SR) Ca(2+)-ATPase with thapsigargin resulted in a significant reduction of the amplitude-frequency relationship of the transient similar to that induced by IL-2. The restitutions were not different between control and IL-2 groups at 1.25 mM [Ca(2+)](o), which was slowed in IL-2-treated myocytes when [Ca(2+)](o) was increased to 2.5 mM. There was no difference in the recirculation fraction (RF) between control and IL-2-treated myocytes at both 1.25 and 2.5 mM [Ca(2+)](o). The effects of IL-2 on frequency relationship, restitution, and RF may be due to depressed SR functions and an increased Na(+)-Ca(2+) exchange activity, but not to any change in L-type Ca(2+) channels.
Cao
C M
CM
Department of Physiology, Zhejiang University School of Medicine, 353 Yan'an Road, Hangzhou 310031, China.
Xia
Q
Q
Bruce
I C
IC
Shen
Y L
YL
Ye
Z G
ZG
Lin
G H
GH
Chen
J Z
JZ
Li
G R
GR
D000251:Adenosine Triphosphatases / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006352:Heart Ventricles / Q000166:cytology; D007376:Interleukin-2 / Q000494:pharmacology*; D008297:Male; D009206:Myocardium / Q000166:cytology; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology; D013050:Spectrometry, Fluorescence; D019284:Thapsigargin / Q000494:pharmacology
D004791:Enzyme Inhibitors; D007376:Interleukin-2; D002110:Caffeine; D019284:Thapsigargin; D000251:Adenosine Triphosphatases; D002118:Calcium