Extracellular nucleotide-induced [Ca2+]i elevation in rat basilar smooth muscle cells.
OBJECTIVE
Extracellular nucleotides play an important role in the regulation of vascular tone and may be involved in cerebral vasospasm after subarachnoid hemorrhage. The objective of this study was to investigate the receptor subtypes for nucleotides and their mechanisms of [Ca2+]i mobilization in cerebral vasculature.


METHODS
Rat basilar smooth muscle cells were isolated by an enzymatic method. [Ca2+]i response, a large transient peak followed by a slowly decaying plateau. The potency of nucleotides to raise [Ca2+]i was ATP gamma S > or = UDP > or = ATP approximately UDP approximately TTP, indicating that P2u receptors were expressed in the rat basilar smooth muscle cells. The effect of UTP to release Ca2+ from internal stores was reduced by pertussis toxin, by the phospholipase C inhibitor 2-nitro-4-carboxyphenyl N,N-diphenylcarbamate, and by the Ca(2+)-pump inhibitor thapsigargin. The Ca2+ entry induced by UTP was partially attenuated by the receptor-operated Ca2+ channel blocker SK&F96365 and by the voltage-dependent Ca2+ channel blocker verapamil. P2 receptor antagonists suramin and, at higher concentrations, pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid reduced the effect of UTP.


CONCLUSIONS
The results are the first demonstration that nucleotides activate G protein-coupled P2u receptors to mobilize [Ca2+]i in rat basilar smooth muscle cells.
Sima
B
B
Department of Surgery, University of Chicago Ill., USA.
Weir
B K
BK
Macdonald
R L
RL
Zhang
H
H
D000818:Animals; D001488:Basilar Artery / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism*; D005260:Female; D005470:Fluorometry; D007425:Intracellular Membranes / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009711:Nucleotides / Q000378:metabolism* / Q000494:pharmacology; D009994:Osmolar Concentration; D058914:Purinergic Antagonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011983:Receptors, Purinergic / Q000502:physiology; D015398:Signal Transduction; D013498:Suramin / Q000494:pharmacology
D009711:Nucleotides; D058914:Purinergic Antagonists; D011983:Receptors, Purinergic; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D013498:Suramin; D002118:Calcium