Intracellular calcium was involved in muscarinic currents increased by hypoosmotic membrane stretch in gastric myocytes of guinea pig.
OBJECTIVE
To investigate the role of intracellular calcium in muscarinic currents increased by hypoosmotic membrane stretch in gastric antral circular myocytes of the guinea pig.


METHODS
The whole cell patch-clamp technique was used, and the myocytes were isolated by collagenase. Cells were swelled by hypoosmotic solution (200 Osmmol/kg).


RESULTS
The hypoosmotic membrane stretch markedly increased carbachol-induced muscarinic currents (ICCh). The ICCh and the increase of ICCh were completely blocked by quinidine 3 micromol/L, a specific muscarinic current blocker. In external calcium-free solution hypoosmotic membrane stretch could not increase ICCh, but in the presence of nicadipine 5 micromol/L, a L-type calcium channel blocker or gadolinium chloride 100 nmol/L, a stretch-activated cation channel blocker, the ICCh was still increased by hypoosmotic membrane stretch. When both nicardipine and gadolinium chloride were added into external solution, ICCh were not increased by hypoosmotic membrane stretch any more. Ryanodine, a calcium-induced calcium release (CICR) agonist completely blocked hypoosmotic membrane stretch-induced increase of ICCh.


CONCLUSIONS
Hypoosmotic membrane stretch increased ICCh and the increment was related to influx of external calcium and CICR.
Yu
Yong-Chun
YC
Research Laboratory of Digestive Physiology, College of Medicine, Yanbian University, Yanji 133000, China.
Guo
Hui-Shu
HS
Piao
Lin
L
Li
Lin
L
Li
Zai-Liu
ZL
Xu
Wen-Xie
WX
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002462:Cell Membrane / Q000502:physiology; D002469:Cell Separation; D005260:Female; D006168:Guinea Pigs; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D018727:Muscarinic Antagonists / Q000494:pharmacology; D032389:Myocytes, Smooth Muscle / Q000502:physiology* / Q000648:ultrastructure; D009529:Nicardipine / Q000494:pharmacology; D009997:Osmotic Pressure; D018408:Patch-Clamp Techniques; D011706:Pyloric Antrum / Q000166:cytology / Q000502:physiology*; D011802:Quinidine / Q000494:pharmacology*; D011976:Receptors, Muscarinic / Q000502:physiology*; D012433:Ryanodine / Q000494:pharmacology
D002121:Calcium Channel Blockers; D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic; D012433:Ryanodine; D002217:Carbachol; D009529:Nicardipine; D011802:Quinidine; D002118:Calcium