Responses of cytosolic free calcium to ADP in platelets of spontaneously hypertensive rats.
Abnormalities of Ca2+ handling have been reported in patients with essential hypertension and in spontaneously hypertensive rats (SHR). In this study, responses of cytosolic Ca2+ to ADP in platelets of SHR were examined. Four- and seven-week-old male SHR and age- and sex-matched Wistar-Kyoto rats (WKY) were used. Basal levels of the intracellular Ca2+ concentration in platelets and responses to ADP were estimated using fluorescent indicator fura-2 in the medium containing 1 mmol/L CaCl2 and Ca2(+)-free buffer with 1 mmol/L EGTA. Basal levels of platelet cytosolic Ca2+ of SHR were significantly higher than those of WKY at 4 and 7 weeks of age in the presence of external Ca2+. However, no significant difference was observed in basal levels of platelet cytosolic Ca2+ in the Ca2(+)-free EGTA-containing buffer between SHR and WKY. The peak cytosolic Ca2+ concentration evoked by ADP was significantly diminished in SHR compared with WKY in the absence of external Ca2+, whereas the responses of platelet cytosolic Ca2+ to ADP were similar in SHR and WKY in the presence of external Ca2+. These results suggest that release from intracellular Ca2+ store is reduced in SHR and that the regulation of cytosolic Ca2+ in SHR is more dependent on extracellular Ca2+ compared with WKY.
Baba
A
A
Department of Medicine, Wakayama Medical College, Japan.
Fukuda
K
K
Hano
T
T
Shiotani
M
M
Yoshikawa
H
H
Ura
M
M
Nakamura
Y
Y
Kuchii
M
M
Nishio
I
I
Masuyama
Y
Y
D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D006973:Hypertension / Q000097:blood*; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D002118:Calcium