Dietary calcium salts as protective agents and laminin P1 as a biochemical marker in chemically induced colon carcinogenesis in rats.

To evaluate the protective effect of different calcium forms against colon carcinogenesis, Wistar rats fed a high-fat diet (24%) were supplemented with different chemical forms of dietary calcium and were intrarectally instilled with N-methyl-N-nitrosourea (NMU). Supplemental calcium was administered at 1.5% mineral (w/w of total diet) complexed with either carbonate, gluconate, or lactate in Groups 2, 3, and 4, respectively. The tumor incidence of colon cancer was compared with a control group (Group 1), fed the same diet without supplemental calcium. Colon carcinoma incidence was 31, 33, 13, and 7% in Groups 1, 2, 3, and 4, respectively. Calcium had a significant protective effect against carcinogenesis, and the maximum protective effect was observed with gluconate and lactate forms. Laminin P1 blood level was measured as a tumor marker. Laminin P1 results were compared with the reference group (Group T), fed a standard diet and not NMU instilled. The serum laminin P1 level was significantly higher (p = 0.0001) in NMU-instilled Groups 1, 2, 3, and 4 (0.24 +/- 0.03, 0.93 +/- 1.43, 0.84 +/- 1.33, and 0.41 +/- 0.34 mU/ml respectively) than in the Reference Group T (0.10 +/- 0.05 mU/ml).