Platelet Ca2+ is not increased in stroke-prone spontaneously hypertensive rats: comparative study with spontaneously hypertensive rats.
We have reported that cytosolic Ca2+ concentration ([Ca2+]i) is increased in platelets from spontaneously hypertensive rats (SHR) in both basal and thrombin-stimulated conditions. To determine whether the correlation between blood pressure and cellular Ca2+ metabolism exists in stroke-prone SHR (SHRSP), we investigated Ca2+ handling using fura 2 and aggregation response in platelets of 12- to 13-week-old male SHRSP, SHR, and Wistar-Kyoto rats (WKY). Systolic pressure was highest in SHRSP and lowest in WKY (213 +/- 8, 172 +/- 7, and 135 +/- 5 mm Hg, respectively). Basal [Ca2+]i was significantly higher in SHR than WKY (45.9 +/- 4.5 versus 41.2 +/- 4.8 nmol/L, P<.05), and that in SHRSP (40.2 +/- 2.8 nmol/L) was similar to that in WKY. Thrombin (0.1 IU/mL)-stimulated [Ca2+]i rise was greater in SHR and smaller in SHRSP than in WKY in the presence of extracellular Ca2+ (530 +/- 50 and 408 +/- 52 versus 475 +/- 50 nmol/L, respectively; P<.05). The recovery rate from the peak [Ca2+]i response to thrombin was greatest in SHRSP and least in WKY. Ionomycin (5 micromol/L)-stimulated [Ca2+]i rise was similar in WKY, SHR, and SHRSP (731 +/- 97, 743 +/- 88, and 683 +/- 70 nmol/L, respectively). Thrombin-induced maximum platelet aggregation response was higher in SHR and lower in SHRSP than WKY (82 +/- 4 percent and 61 +/- 15 percent versus 73 +/- 6 percent, respectively; P<.05). In contrast to SHR, basal [Ca2+]i in SHRSP was similar to that in WKY, and thrombin-stimulated [Ca2+]i was attenuated. These result suggest that platelet Ca2+ handling differs between SHR substrains and that an increased [Ca2+]i is not obligatory in genetically hypertensive rats.
Ono
N
N
First Department of Internal Medicine, Hiroshima University School of Medicine, Japan.
Oshima
T
T
Ishida
M
M
Ishida
T
T
Matsuura
H
H
Kambe
M
M
Kajiyama
G
G
D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D001794:Blood Pressure; D002118:Calcium / Q000097:blood / Q000378:metabolism*; D002561:Cerebrovascular Disorders / Q000097:blood*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D006973:Hypertension / Q000097:blood*; D015759:Ionomycin / Q000494:pharmacology; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013917:Thrombin / Q000494:pharmacology
D015759:Ionomycin; D013917:Thrombin; D002118:Calcium; D016257:Fura-2