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(Hypertension. 2001;37:1129.)
© 2001 American Heart Association, Inc.

Scientific Contributions

Abnormal Platelet Function and Calcium Handling in Dahl Salt-Hypertensive Rats

Yun Li; Takeshi Adachi; Victoria M. Bolotina; Cathy Knowles; Kenneth A. Ault; Richard A. Cohen

From the Vascular Biology Unit, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Mass (Y.L., T.A., V.M.B., R.A.C); and Maine Medical Center Research Institute, South Portland, Maine (C.K., K.A.A.).

Correspondence to Dr Richard A. Cohen, Vascular Biology Unit, EBRC 7, Boston University School of Medicine, 650 Albany St, Boston, MA 02118. E-mail racohen{at}medicine.bu.edu

Abstract—The effect of dietary salt on platelet function and Ca²⁺ homeostasis was studied in Dahl (DS) rats, a genetic model of salt-sensitive hypertension. DS rats were fed a high-salt (DSHS) or a low-salt diet (DSLS) for up to 4 weeks, and the effects of salt loading on systolic blood pressure, platelet P-selectin expression, and platelet Ca²⁺ homeostasis were measured. The high-salt diet increased blood pressure and markedly increased the amount of ionomycin (IM)-releasable Ca²⁺ in platelet intracellular stores (Ca²⁺/IM). The alteration in Ca²⁺ stores was not prevented when the hypertension was prevented by treatment with hydralazine and reserpine. The Ca²⁺ store filling during platelet exposure to 1 mmol/L Ca²⁺ for 5 minutes and the rate of sarcoplasmic/endoplasmic Ca²⁺ ATPase–dependent Ca⁴⁵ uptake were higher in DSHS compared with that in DSLS. There was a decrease in thrombin-induced Ca²⁺ influx in platelets from DSHS; consistent with this, agonist-induced P-selectin expression was decreased. In DSLS, nitric oxide accelerated reloading of platelet Ca²⁺ stores after their emptying by thrombin but failed to do so in DSHS. These results indicate that in DS rats, a high-salt diet increases sarcoplasmic/endoplasmic Ca²⁺ ATPase activity and the Ca²⁺/IM but decreases the reuptake of Ca²⁺ caused by nitric oxide. Decreases in Ca²⁺ influx and platelet P-selectin expression might be explained by changes in intracellular Ca²⁺ stores in DSHS rats, which apparently is a heritable response to a high-salt diet.

Key Words: salt • calcium • diet • nitric oxide • rats, Dahl • platelets