Characterisation of the Lysosomal Heterogeneity in Chinese-Hamster Fibroblasts

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Abstract
1 Homogenates of Chinese hamster fibroblasts have been fractionated by analytical centrifugation techniques. Lysosomes have been characterised and identified by the distinctive behaviour of specific marker constituents. 2 The acid hydrolases of hamster fibroblasts were located in two distinct organelles, characterised by differences in their equilibrium densities and rates of sedimentation. The lighter population of lysosomes with a modal density of 1.10 g cm−3, contained glycosidases, nucleases and acid phosphatase. The denser population, with a modal density of 1.15 g cm−3, contained proteases and arylsulphatase B. 3 Acid hydrolases in both populations showed similar degrees of latency and structure-linked sedimentability. 4 The heterophagic activity of hamster fibroblasts was investigated by growing the cells in the presence of [14C]sucrose, [14C]inulin and Triton WR 1339. These compounds are taken up by the cells and appear to be located in the denser population of lysosomes. 5 The low density of the lighter population of lysosomes appears to result from a high content of cholesterol esters and triacylglycerols. It is suggested that the lysosomes may be the site of storage of a considerable proportion of these lipids in cultured hamster cells