Binding of collagen causes intracellular mobilization of calcium in human mononuclear cells

The possibility that extracellular matrix-cell surface interaction might lead to signalling was examined in human mononuclear cells. In mononuclear cells loaded with Indo-1 acetoxymethylester, collagen binding elicited a 2-3 fold increase in cytosolic free calcium concentration within seconds. Plasma fibronectin, serum albumin and heparin did not cause any significant change in intracellular calcium levels. Collagen I, collagen IV and glucosylated collagen I evoked an increase in intracellular Ca++ both in the presence and absence of extracellular calcium. However, in the presence of 2mM EDTA, the increase in cytosolic free calcium concentration caused by collagen I and collagen IV was partly abolished, suggesting the requirement of a cation-dependent interaction of collagen with mononuclear cells. Glucosylated collagen induced intracellular calcium mobilization even in the presence of EDTA suggesting a cation-independent interaction. These results indicate that collagen binding induces rapid mobilization of calcium in human mononuclear cells, apparently from intracellular sources.