Fluorescence digital image analysis of serotonin-induced calcium oscillations in single blood platelets.
The intracellular concentration of Ca2+ [( Ca2+]i) was monitored continuously in single rabbit blood platelets by digital imaging microscopy in conjunction with Fura-2, a specific Ca(2+)-indicator dye. Ionomycin as well as aluminium fluoride caused sustained increase in [Ca2+]i in the platelet, but oscillations of [Ca2+]i were not observed. Serotonin (5-HT) induced oscillatory increases in [Ca2+]i in the presence of 1 mM CaCl2; these had not been detectable in cell populations because the oscillations were not in synchrony. This effect of 5-HT was diminished when CaCl2 was omitted from the medium, and was antagonized by 1 microM ketanserin, a specific 5-HT2 receptor antagonist. Furthermore, DOI, a specific 5-HT2 agonist, had the same effect as 5-HT at lower concentration. A specific effector mechanism, not fully understood at present, therefore appears to mediate 5-HT2 receptors thereby allowing rabbit platelets to generate [Ca2+]i oscillations. It is suggested that protein kinase C in platelets might play a key role in the regulation of [Ca2+]i, and possibly in [Ca2+]i oscillations.
Nishio
H
H
Department of Pharmacology, Hiroshima University School of Medicine, Japan.
Ikegami
Y
Y
Segawa
T
T
D000535:Aluminum / Q000494:pharmacology; D017607:Aluminum Compounds; D000662:Amphetamines / Q000494:pharmacology; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects; D004224:Diterpenes; D005459:Fluorides / Q000494:pharmacology; D016257:Fura-2; D007091:Image Processing, Computer-Assisted; D015759:Ionomycin / Q000494:pharmacology; D007650:Ketanserin / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D010507:Periodicity; D011817:Rabbits; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013729:Terpenes / Q000494:pharmacology
D017607:Aluminum Compounds; D000662:Amphetamines; D004224:Diterpenes; D012702:Serotonin Antagonists; D013729:Terpenes; D012701:Serotonin; C011309:mezerein; D015759:Ionomycin; D007650:Ketanserin; D000535:Aluminum; C015952:4-iodo-2,5-dimethoxyphenylisopropylamine; D005459:Fluorides; D002118:Calcium; D016257:Fura-2; C032311:aluminum fluoride