Changes in Ca2+ mobilization in platelets from stroke-prone spontaneously hypertensive rats.
Intracellular free Ca2+, [Ca2+]i, levels were measured in platelets from stroke-prone spontaneously hypertensive rats (SHRSP) and normotensive Wistar-Kyoto rats (WKY) using fura-2AM. In the presence of extracellular Ca2+ (1 mM), [Ca2+]i levels in unstimulated platelets of 2- and 9-month-old SHRSP were both significantly higher than those of the age matched WKY. In the absence of extracellular Ca2+, the levels in platelets from 9-month-old SHRSP were also higher than any other groups examined. Receptor-linked Ca2+ influxes of old SHRSP were smaller when thrombin or collagen was given to the platelets. Phorbol 12-myristate 13-acetate (TPA) enhanced more prominently the Ca2+ influx into old SHRSP platelets than into old WKY platelets. These results strongly suggest that the Ca2+ permeability across plasma membrane is increased in young as well as old SHRSP platelets, where the resting [Ca2+]i level is highly sustained because of an impaired Ca2+ uptake mechanism and possible enhancement of protein kinase C activity.
Higashino
H
H
Department of Pharmacology, Kinki University School of Medicine, Osaka-Sayama, Japan.
Suzuki
A
A
D000818:Animals; D001792:Blood Platelets / Q000737:chemistry* / Q000187:drug effects; D002118:Calcium / Q000097:blood*; D003094:Collagen / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D008297:Male; D051381:Rats; D011918:Rats, Inbred SHR / Q000097:blood*; D011921:Rats, Inbred WKY; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology
D015759:Ionomycin; D003094:Collagen; D013917:Thrombin; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium