title: Dietary calcium attenuates platelet aggregation and intracellular Ca2+ mobilization in spontaneously hypertensive rats.
abstract: Spontaneously hypertensive rats (SHR) are known to be blood pressure sensitive to dietary calcium. The effects of dietary calcium on platelet aggregation and intracellular Ca2+ mobilization were assessed by turbidimetric methods and fura-2 methods, respectively, in washed platelets of SHR. Ca2+ ATPase activity was examined in aortic membrane fractions. Six weeks of dietary calcium supplementation attenuated the increase of systolic blood pressure (SBP 199 +/- 16 v 170 +/- 9 mm Hg, P < .001) and thrombin-induced platelet aggregation (84.5 +/- 3.7 v 73.7 +/- 7.4%, P < .004) at 9 weeks of age. The ionomycin-induced intracellular calcium ([Ca2+]i) peak in the absence of external Ca2+, which reflects [Ca2+]i storage size, and thrombin-evoked [Ca2+]i release from [Ca2+]i storage were decreased by 2.0% Ca diet (472 +/- 55 v 370 +/- 23 nmol/L, P < .001, 339 +/- 29 v 278 +/- 33 nmol/L, P < .002). In addition, SBP was positively correlated with platelet aggregation (r = 0.703, P = .0088), thrombin-evoked [Ca2+]i (r = 0.739, P = .0044), and ionomycin-induced [Ca2+]i (r = 0.591, P = .0415), respectively. However, there was no significant effect of dietary calcium on Ca2+-ATPase activity in aortic membranes. These results suggest that dietary calcium supplementation had a beneficial effect on platelets of SHR by attenuating [Ca2+]i mobilization from [Ca2+]i storage. The hypotensive effect of dietary calcium might be associated with attenuated [Ca2+]i mobilization in SHR.
authors.affiliation: Department of Medicine, Oregon Health Sciences University, Portland 97201-3098, USA.
authors.forename: K
authors.initials: K
authors.lastname: Otsuka
authors.forename: M
authors.initials: M
authors.lastname: Watanabe
authors.forename: Q
authors.initials: Q
authors.lastname: Yue
authors.forename: D A
authors.initials: DA
authors.lastname: McCarron
authors.forename: D
authors.initials: D
authors.lastname: Hatton
mesh_terms: D000818:Animals; D001011:Aorta / Q000201:enzymology; D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002136:Calcium, Dietary / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D006973:Hypertension / Q000097:blood*; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects*; D051381:Rats; D011918:Rats, Inbred SHR
chemical_list: D002136:Calcium, Dietary; D000252:Calcium-Transporting ATPases; D002118:Calcium