Intracellular calcium mobilization in rat platelets is adversely affected by copper deficiency.
The influence of copper deficiency on the mobilization of Ca2+ from intracellular stores following ionomycin treatment or thrombin activation of rat platelets was examined using the fluorescent indicator, fura-2, to measure changes in cytosolic Ca2+ concentration ([Ca2+]i). Platelets, obtained from copper-deficient and control rats and loaded with fura-2, were suspended in medium containing 1 mM EGTA and no added Ca2+. The size of the internal Ca2+ pools in the suspended platelets was estimated from the rise in [Ca2+]i following maximal discharge of stored Ca2+ by treatment with 1 microM ionomycin. Peak [Ca2+]i following ionomycin treatment was lower in platelets from copper-deficient rats compared to control rats (148 +/- 27 nM vs. 188 +/- 17 nM), suggesting that the size of the Ca2+ storage pools was decreased by copper deficiency. Furthermore, once internal Ca2+ stores were discharged by ionomycin, [Ca2+]i remained elevated in platelets from copper-deficient rats, but decreased in control rats. These data indicate that copper deficiency may inhibit the efflux of Ca2+ from platelets after its release from internal stores by ionomycin treatment. In platelets from copper-deficient and control rats, stimulation with 0.1 U/ml thrombin led to rapid rise followed by a slow decay in [Ca2+]i. However, peak [Ca2+]i was lower in platelets from copper-deficient rats than in control rats (94 +/- 19 nM vs. 131 +/- 16 nM). These findings imply that by reducing the amount of Ca2+ available for release from intracellular stores, copper deficiency also reduces [Ca2+]i following thrombin activation in the absence of external Ca2+.
Johnson
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WT
United States Department of Agriculture, Grand Forks Human Nutrition Research Center, ND 58202.
Dufault
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D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D003300:Copper / Q000172:deficiency*; D003600:Cytosol / Q000378:metabolism; D004032:Diet; D015759:Ionomycin / Q000494:pharmacology; D008297:Male; D015539:Platelet Activation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013917:Thrombin / Q000494:pharmacology
D015759:Ionomycin; D003300:Copper; D013917:Thrombin; D002118:Calcium