Heat stress responses modulate calcium regulations and electrophysiological characteristics in atrial myocytes.
Heat stress-induced responses change the ionic currents and calcium homeostasis. However, the molecular insights into the heat stress responses on calcium homeostasis remain unclear. The purposes of this study were to examine the mechanisms of heat stress responses on calcium handling and electrophysiological characteristics in atrial myocytes. We used indo-1 fluorimetric ratio technique and whole-cell patch clamp to investigate the intracellular calcium, action potentials, and ionic currents in isolated rabbit single atrial cardiomyocytes with or without (control) exposure to heat stress (43 degrees C, 15 min) 5+/-1 h before experiments. The expressions of sarcoplasmic reticulum ATPase (SERCA2a), and Na(+)-Ca(2+) exchanger (NCX) in the control and heat stress-treated atrial myocytes were evaluated by Western blot and real-time PCR. As compared with control myocytes, the heat stress-treated myocytes had larger sarcoplasmic reticulum calcium content and larger intracellular calcium transient with a shorter decay portion. Heat stress-treated myocytes also had larger L-type calcium currents, transient outward potassium currents, but smaller NCX currents. Heat stress responses increased the protein expressions, SERCA2a, NCX, and heat shock protein. However, heat stress responses did not change the RNA expression of SERCA2a and NCX. In conclusion, heat stress responses change calcium handling through protein but not RNA regulation.
Chen
Yao-Chang
YC
Department of Biomedical Engineering, National Defense Medical Center, Taipei, Taiwan.
Kao
Yu-Hsun
YH
Huang
Chun-Feng
CF
Cheng
Chen-Chuan
CC
Chen
Yi-Jen
YJ
Chen
Shih-Ann
SA
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004594:Electrophysiology / Q000379:methods; D005470:Fluorometry / Q000379:methods; D006325:Heart Atria / Q000166:cytology; D006706:Homeostasis; D006358:Hot Temperature; D007211:Indoles / Q000494:pharmacology; D007477:Ions; D032383:Myocytes, Cardiac / Q000166:cytology*; D018408:Patch-Clamp Techniques; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism
D007211:Indoles; D007477:Ions; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; C048960:indo-1; D002118:Calcium