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(Hypertension. 1996;27:1312-1317.)
© 1996 American Heart Association, Inc.
Articles |
Platelet Ca2+ Is Not Increased in Stroke-Prone Spontaneously Hypertensive Rats
Comparative Study With Spontaneously Hypertensive Rats
From the First Department of Internal Medicine (N.O., M.I., T.I., H.M., G.K.) and Department of Clinical Laboratory Medicine (T.O., M.K.), Hiroshima (Japan) University School of Medicine.
Correspondence to Norihisa Ono, MD, First Department of Internal Medicine, Hiroshima University School of Medicine, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734, Japan.
Abstract 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 µmol/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% and 61±15% versus 73±6%, 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 results suggest that platelet Ca2+ handling differs between SHR substrains and that an increased [Ca2+]i is not obligatory in genetically hypertensive rats.
Key Words: calcium • fura-2 • platelet aggregation • rats, inbred SHR • rats, inbred, SHRSP
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