Effect of ethanol on spontaneous phasic contractions of cat gastric smooth muscle.
BACKGROUND
Ethanol is generally believed to inhibit extracellular Ca2+ influx, thereby inhibiting gastric muscle contraction. Recently, we observed that verapamil inhibited only the amplitude of spontaneous phasic contractions, whereas ethanol inhibited both amplitude and frequency. In our objective to investigate the mechanism of ethanol's inhibition of gastric motility, the involvement of various protein kinases in ethanol-inhibited spontaneous phasic contractions of the stomach muscle strips was tested.


METHODS
Circular muscle strips (2.0 x 0.2 cm) were prepared from the corpus of cat stomach in order to measure isometric contraction in a chamber filled with Krebs-Ringer solution (pH 7.4, temperature 36 degrees C) bubbled with 5% CO2 in O2.


RESULTS
Spontaneous phasic contraction was not affected by various receptor antagonists (I microM atropine, 1 microM hexamethonium, 1 microM phentolamine and 1 microM propranolol) or 1 microM tetrodotoxin. EGTA and verapamil dose-dependently inhibited only the amplitude of spontaneous phasic contractions and not the frequency. Ethanol dose-dependently inhibited both the amplitude and frequency of phasic contractions. The amplitude and frequency of spontaneous phasic contractions were significantly inhibited by protein kinase C and tyrosine kinase inhibitors. However, neither protein kinase C activator nor various phosphatase inhibitors blocked the inhibitory effect of ethanol.


CONCLUSIONS
Ethanol appears to inhibit spontaneous phasic contractions by a mechanism other than the inhibition of protein kinase C or tyrosine kinase or the inhibition of extracellular Ca2+ influx.
Sim
S S
SS
Dept of Physiology, College of Medicine, The Catholic University of Korea, Socho-gu, Seoul.
Choi
J C
JC
Min
D S
DS
Rhie
D J
DJ
Yoon
S H
SH
Hahn
S J
SJ
Kim
C J
CJ
Kim
M S
MS
Jo
Y H
YH
D000818:Animals; D002415:Cats; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000494:pharmacology*; D005260:Female; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology; D007537:Isometric Contraction / Q000187:drug effects* / Q000502:physiology; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects* / Q000503:physiopathology; D011494:Protein Kinases / Q000494:pharmacology; D013270:Stomach / Q000187:drug effects* / Q000503:physiopathology; D013997:Time Factors
D002492:Central Nervous System Depressants; D000431:Ethanol; D011494:Protein Kinases