Mechanisms of hemolysate-induced [Ca2+]i elevation in cerebral smooth muscle cells.
The effects of hemolysate on free cytosolic [Ca2+] ([Ca2+]i) homeostasis were studied in freshly isolated rat basilar artery smooth muscle cells using fura 2 and dual excitation wavelength microfluorimetry. Hemolysate reversibly produced a transient [Ca2+]i peak followed by a slowly decaying plateau which was absent in Ca(2+)-free solution. This effect of hemolysate was attenuated by 1) the sarcoplasmic reticulum Ca2+ pump inhibitors thapsigargin and cyclopiazonic acid, 2) the Ca2+ release-blocking agents ryanodine and dantrolene, 3) the cytochrome P-450 inhibitor econazole, and 4) the inorganic Ca2+ channel blocker lanthanum but was not significantly attenuated by 1) the receptor-regulated Ca2+ channel blocker SKF-96365 or 2) the voltage-dependent Ca2+ channel blocker nimodipine. Fractionation of hemolysate using membranes with specific pore sizes (0.5, 1, and 12-14 kDa) indicated that a component(s) > 0.5 but < 1 kDa could produce a similar [Ca2+]i peak and plateau while fractions > 1 and > 12-14 kDa produced a small and slow [Ca2+]i rise without a significant peak. ATP, which was found in hemolysate, produced a [Ca2+]i response similar to that of hemolysate. P2-purinoceptor antagonists significantly attenuated the effect of ATP, hemolysate, and the fractions < 1 and < 12-14 kDa. We conclude that hemolysate elevates [Ca2+]i by both releasing Ca2+ from internal stores and triggering Ca2+ entry, possibly from a voltage-independent Ca2+ influx pathway, an effect apparently identical to that of ATP.
Zhang
H
H
Department of Surgery, University of Chicago, Illinois 60637, USA.
Weir
B
B
Marton
L S
LS
Macdonald
R L
RL
Bindokas
V
V
Miller
R J
RJ
Brorson
J R
JR
D019794:2,3-Diphosphoglycerate; D000818:Animals; D001488:Basilar Artery / Q000166:cytology / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism*; D004163:Diphosphoglyceric Acids / Q000494:pharmacology; D005260:Female; D006461:Hemolysis; D006706:Homeostasis; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009711:Nucleotides / Q000494:pharmacology; D009994:Osmolar Concentration; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013498:Suramin / Q000494:pharmacology
D002121:Calcium Channel Blockers; D004163:Diphosphoglyceric Acids; D009711:Nucleotides; D019794:2,3-Diphosphoglycerate; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D013498:Suramin; D002118:Calcium