Table 2.

Effect of replicative aging on lysosomal hydrolases.

	Low passages			High passages
	β-Gal (pH 6)	β-Gal (pH 4)	β-Gluc	β-Gal (pH 6)	β-Gal (pH 4)	β-Gluc
CF	6.30 ± 0.4	24.88 ± 4.6	4.22 ± 0.5	7.97 ± 0.7	23.42 ± 2.2	6.54 ± 0.7a
T21F	7.42 ± 0.9	23.68 ± 2.3	4.53 ± 0.7	8.19 ± 0.6	21.05 ± 2.0	5.96 ± 0.7

Activities of lysosomal enzymes, β-galactosidase, and β-glucuronidase in cell homogenates of control (n = 5) and trisomy 21 (n = 5) fibroblasts at low and high passages. Activities were corrected by the protein content of the cellular homogenates. The β-galactosidase activity was determined at pH 4.0 and 6.0. Results are expressed as mean ± SEM. Statistical differences between passages were analyzed with Student's t-test: ^a P < 0.05.