Lack of increase in platelet Ca2+ and Na+ in deoxycorticosterone acetate-salt hypertensive rats.
We have previously characterized abnormal Ca2+ handling in platelets of spontaneously hypertensive rats (SHRs). In this study, we investigated whether cellular Ca2+ metabolism and/or Na+ concentration is altered in platelets of deoxycorticosterone acetate-salt hypertensive rats (DOCA rats). The resting cytosolic Ca2+ concentration ([Ca2+]i) in platelets was significantly lower in DOCA rats than controls (54.5 +/- 1.4 vs. 61.2 +/- 2.3 nmol/l). The amplitude of the [Ca2+]i transient induced by thrombin was significantly increased in the absence, but not the presence, of external Ca2+ in DOCA rats compared with control rats. The [Ca2+]i response to 5 mumol/l ionomycin in the Ca(2+)-free buffer was greater in DOCA rats than in controls (546 +/- 23 vs. 470 +/- 18 nmol/l), indicating larger intracellular Ca2+ stores. The rate of recovery of [Ca2+]i after the peak response to thrombin was decreased in DOCA rats (79% at 0.1 U/ml and 91% at 1.0 U/ml thrombin of control rats). Cytosolic Na+ concentration ([Na+]i) in platelets was similar in DOCA and control rats. Altered Ca2+ levels are not correlated with [Na+]i in this salt-sensitive hypertensive model. Therefore, an increased [Ca2+]i is not an obligatory phenomenon in hypertension.
First Department of Internal Medicine, Hiroshima University School of Medicine, Japan.
M
M
Ishida
T
T
Ishida
H
H
Matsuura
R
R
Ozono
G
G
Kajiyama
T
T
Oshima
D000818:Animals; D001572:Benzofurans; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002118:Calcium / Q000097:blood*; D003600:Cytosol / Q000378:metabolism; D003900:Desoxycorticosterone / Q000494:pharmacology; D004988:Ethers, Cyclic; D005456:Fluorescent Dyes; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000097:blood* / Q000139:chemically induced / Q000503:physiopathology; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012016:Reference Values; D012964:Sodium / Q000097:blood*; D012982:Sodium, Dietary / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology
D001572:Benzofurans; D004988:Ethers, Cyclic; D005456:Fluorescent Dyes; D012982:Sodium, Dietary; C061665:sodium-binding benzofuran isophthalate; D003900:Desoxycorticosterone; D012964:Sodium; D013917:Thrombin; D002118:Calcium