1. The cytoplasmic free calcium concentration ([Ca2+]i) in the platelets of spontaneously hypertensive rats (SHR), Wistar–Kyoto rats (WKY), deoxycorticosterone–salt hypertensive rats (DOC) and normotensive Sprague–Dawley rats (SD) was measured with the fluorescent dye, quin-2-tetra-acetoxymethyl ester.
2. No significant difference in platelet [Ca2+]i was found between SHR and WKY or between DOC and SD rats.
3. No correlations were found between systolic blood pressure and [Ca2+]i.
4. These results suggest that the elevation of platelet [Ca2+]i does not necessarily accompany hypertension in rats.