Compromised Zinc Status in Rats Adversely Affects Calcium Metabolism in Platelets

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Abstract
The effect of zinc status on external calcium uptake by rat platelets and the relation of uptake to aggregation malfunction were studied. For 11 d, immature male rats were fed either a low zinc diet (0.3 mg/kg) ad libitum, a zinc-adequate diet (100 mg/kg) ad libitum, or the adequate diet pair-fed. Washed platelets were loaded with fura-2 acetoxymethyl ester for measurement of cytosolic free calcium. The resting calcium concentration was higher in platelets from rats of low zinc status than in those from controls. When platelets were stimulated with a minimal level (0.12 µmol/L) of ADP, the free cytosolic calcium concentration increased to a greater extent when calcium was present in the external medium than in its absence. The difference was considered to be external uptake. Zinc status had no effect on internal release, but platelets from zinc-deficient rats took up significantly less external calcium. In conclusion, low zinc status in rats adversely affects calcium metabolism in platelets. Decreased uptake of external calcium by ADP-stimulated platelets is associated with defective aggregation.