Contractile responses in human umbilical arteries to hyper- and hypotonic solutions.
The effects of hyper- and hypotonic solutions on vascular smooth muscle were studied using helical strips from human umbilical arteries. Hypertonic solutions evoked a biphasic contraction that consisted of early and late contractions. Verapamil or Ca(2+)-free conditions inhibited early contraction induced by tonicity of 340-539 mosm/kg. Under these conditions, late contraction induced by 340-407 mosm/kg was inhibited, whereas contraction induced by 539 mosm/kg was not. Hypotonic solutions evoked a monophasic contraction. Verapamil or Ca(2+)-free conditions inhibited contraction induced by tonicity of 249-266 mosm/kg but not by tonicity of 213 mosm/kg. Hyper- or hypotonicity-induced contractions were not affected by the presence or absence of endothelium. These results suggest that a small increase or decrease in tonicity within the pathophysiological range of osmotic pressure (260-340 mosm/kg) evokes contraction in human umbilical arteries by stimulating calcium influx through voltage-sensitive Ca2+ channels.
Second Department of Internal Medicine, Nagoya City University Medical School, Japan.
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K
Sato
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Kojima
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Y
Dohi
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D006801:Humans; D006982:Hypertonic Solutions / Q000494:pharmacology*; D007038:Hypotonic Solutions / Q000494:pharmacology*; D008297:Male; D009997:Osmotic Pressure; D051381:Rats; D017208:Rats, Wistar; D014469:Umbilical Arteries / Q000187:drug effects* / Q000502:physiology; D014661:Vasoconstriction; D014700:Verapamil / Q000494:pharmacology
D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D014700:Verapamil; D002118:Calcium