Ovariectomy aggravated sodium induced hypertension associated with altered platelet intracellular Ca2+ in Dahl rats.
Our purpose was to determine the effect of ovariectomy on intracellular Ca2+ mobilization and platelet aggregation in sodium induced hypertension. At the age of 12 weeks ovariectomy or sham operation was performed in female Dahl-Iwai salt sensitive rats on a 0.3% NaCl diet. Four weeks later we assessed the effects of ovariectomy and an 8% NaCl diet on agonist induced intracellular Ca2+ mobilization in fura-2 loaded platelets and platelet aggregation. Ovariectomy enhanced the increase of systolic blood pressure and heart to body weight ratio on an 8% NaCl diet. However, thrombin evoked intracellular Ca2+ was not correlated with systolic blood pressure (r = -0.338, P = .17), and was lowered by sodium loading and ovariectomy (360+/-23 to 285+/-9, 296+/-10 nmol/L, P < .05). Furthermore, the ionomycin induced intracellular calcium fraction in the absence of external Ca2+ that reflected internal Ca2+ discharge capacity was reduced in ovariectomized rats compared with sham operated rats on an 8% NaCl diet (648+/-15 v 768+/-35 nmol/L, P < .05). The internal Ca2+ discharge capacity was inversely correlated with systolic blood pressure (r = -0.506, P = .03). In addition to the decreased internal Ca2+ discharge capacity, intracellular Ca2+-independent platelet aggregation by phorbol 12-myristate 13-acetate, a protein kinase C activator, was significantly enhanced in hypertensive rats. We concluded that ovariectomy enhanced sodium induced hypertension associated with the decreased internal Ca2+ discharge capacity and increased platelet aggregation in Dahl-Iwai salt-sensitive rats.
Otsuka
K
K
Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan.
Ohno
Y
Y
Sasaki
T
T
Yamakawa
H
H
Hayashida
T
T
Suzawa
T
T
Suzuki
H
H
Saruta
T
T
D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D005260:Female; D006973:Hypertension / Q000097:blood / Q000209:etiology* / Q000378:metabolism; D010052:Ovariectomy; D010974:Platelet Aggregation; D051381:Rats; D012982:Sodium, Dietary / Q000008:administration & dosage*
D012982:Sodium, Dietary; D002118:Calcium