Observations on the use of a cation exchange resin for the preparation of metal-depleted media for lymphocyte culture

A chelating resin specific for divalent cations (Chelex) was used to prepare metal-depleted media for lymphocyte culture. A batch procedure (resin in pH 7.4 phosphate buffer/specimen, 1:1) removed 70–80% of iron, 77–87% of copper and 88–98% of zinc, calcium and magnesium. At variance with other reports, when a resin/specimen ratio of 1:4 was used, iron chelation decreased to 40%, whereas other cation chelation remained unchanged. Best chelation for iron and calcium was obtained at pH 5–6.4; for copper, zinc and magnecium, at pH 7.4–8.0. During the procedure protein content decreased by 8–10%; arginine and lysine by 80%; asparagine, cystine, tyrosine and phenylalanine by 60%, other amino acids by 35% These new data suggest that the cation-depleted media prepared with Chelex may be used to study the effects of cations on lymphocytes in culture, provided that the most appropriate pH and resin/specimen ratio are selected and adequate amino acid replacement is performed. Results on normal human lymphocytes are reported.