Abnormal platelet and lymphocyte calcium handling in prehypertensive rats.
We have reported that the basal and stimulated cytosolic free calcium concentrations [( Ca2+]i) are elevated in platelets isolated from 12-14-week-old spontaneously hypertensive rats (SHR) as compared with normotensive Wistar-Kyoto (WKY) rats. To determine whether altered cell calcium metabolism precedes the development of overt hypertension, we measured [Ca2+]i under resting and stimulated conditions in blood platelets and thymic lymphocytes isolated from 4-week-old prehypertensive SHR and WKY rats. Blood pressure was similar in both groups (SHR 95 +/- 8 versus WKY rats 92 +/- 7 mm Hg). Basal [Ca2+]i in platelets was higher in SHR than WKY rats (63.4 +/- 3.9 versus 54.8 +/- 3.1 nM, p less than 0.003). Also the [Ca2+]i response to thrombin was greater in SHR than WKY rats in both the presence and absence of extracellular calcium. For lymphocytes, although no difference was detected in basal [Ca2+]i, the concanavalin A-induced peak [Ca2+]i was higher for SHR than WKY rats in both calcium-containing and calcium-free media. These results suggest that agonist-stimulated calcium influx and calcium discharge from intracellular stores are enhanced in both platelets and lymphocytes of 4-week-old SHR. We conclude that abnormalities in calcium metabolism in two different cell types precede the development of overt hypertension in the SHR.
Oshima
T
T
Division of Nephrology and Hypertension, Oregon Health Sciences University, Portland 97201.
Young
E W
EW
McCarron
D A
DA
D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D003208:Concanavalin A / Q000494:pharmacology; D006973:Hypertension / Q000209:etiology* / Q000378:metabolism; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013917:Thrombin / Q000494:pharmacology
D003208:Concanavalin A; D013917:Thrombin; D002118:Calcium