ATP and ACh induced CICR in outer hair cells of the guinea pig cochlea: study of confocal microscopy.
- Author:
Li HUANG
1
;
Jun YANG
Author Information
1. Department of Otolaryngology-Head and Neck Surgery, Xinhua Hospital Jiaotong University School of Medicine, Shanghai, 200092, China.
- Publication Type:Journal Article
- MeSH:
Acetylcholine;
pharmacology;
Adenosine Triphosphate;
pharmacology;
Animals;
Calcium;
metabolism;
Calcium Channels;
drug effects;
metabolism;
Cells, Cultured;
Cochlea;
cytology;
metabolism;
Guinea Pigs;
Hair Cells, Auditory, Outer;
metabolism;
Microscopy, Confocal;
Ryanodine;
pharmacology;
Thapsigargin;
pharmacology
- From:
Journal of Clinical Otorhinolaryngology Head and Neck Surgery
2009;23(7):316-321
- CountryChina
- Language:Chinese
-
Abstract:
OBJECTIVE:Effects of ATP and acetylcholine (ACh) on intracellular Ca2+ concentrations ([Ca2+]i) and possible mechanism of Ca2+-induced Ca2+ release (CICR) of the isolated outer hair cells (OHCs) in the guinea pig cochlea were studied with confocal microscopy.
METHOD:OHCs were isolated from guinea pig cochlea by enzymatic and mechanical methods. The effects of ATP, ACh, Ryanodine + ATP (or ACh) and Thapsigargin + ATP (or ACh) in the presence or absence of extracellular Ca2+ on [Ca2+]i in OHCs were examined by confocal microscopy.
RESULT:In the presence of ATP, Ryanodine + ATP, Thapsigargin + ATP, ACh, Ryanodine + ACh and Thapsigargin + ACh increased [Ca2+]i and evoked an evident wave, respectively, the relative magnitude of fluorescence were 1.60 +/- 0.01(ATP), 1.644 +/- 0.005 (Ryanodine + ATP), 1.491 +/- 0.005 (Thapsigargin + ATP), 1.43 +/- 0.01 (ACh), 1.58 +/- 0.02 (Ryanodine + ACh), 1.398 +/- 0.003 (Thapsigargin + ACh) in OHCs in the presence of extracellular Ca2+ respectively. In the absence of extracellular Ca2+, ATP and Ryanodine + ATP induced a gradual and small [Ca2+]i wave, the relative magnitude of fluorescence were 1.341 +/- 0.006 and 1.386 +/- 0.008, however, ACh, Ryanodine + ACh, Thapsigargin + ACh and Thapsigargin + ATP can not induce wave but a gradual [Ca2+]i elevation. ACh can not increase [Ca2+]i.
CONCLUSION:In the presence of extracellular Ca2+, ATP and ACh increased [Ca2+]i in OHCs not only by Ca2+ influx through ion channel on cell membrane but also a release of Ca2+ from IP3-sensitive calcium reservoir and CICR. In the absence of extracellular Ca2+, ATP activated IP3 sensitive calcium reservoir and Ca2+ release through IP3 sensitive calcium reservoir, in turn CICR was induced. ACh can not activate IP3 sensitive calcium reservoir and CICR in the absence of extracellular Ca2+, therefore, the effect of ACh was dependent of extracellular Ca2+.
