Abstract
Abstract
The activity of S'nucleotidase was investigated in rabbit chondrocytes. Studies of chondrocytes in organ culture and intact cells revealed that ecto-5′nucleotidase activity varies with the age of the animal. Specific activites of 0.29, 0.62, 1.97, and 1.39 μmole/hr/106 cells were observed in intact cells from 3-week-, 3-month-, 6-month-, and 2-year-old animals. Specific activities of 15.5, 33.1, 80.3, and 39.5 μmole/hr/mg protein, respectively, were observed when the enzyme protein was solubilized from disrupted cells with the detergent octyl-β-D-glucopyranoside. Membrane-bound nonspecific neutral phosphatase activity did not vary with age. Activity of 5′nucleotidase was observed on all chondrocytes using a histochemical staining technique. Kinetic properties of the enzyme from animals of different ages were investigated. No differences were noted in apparent K m value for AMP (23 μA/), pH optima (7.3), substrate competition studies, and effects of MgCl2 or CaCl2. These data demonstrate a biological variation in rabbit chondrocyte 5′nucleotidase activity with age. The variation of activity represents an apparent increase in the amount of enzyme protein rather than an alteration in kinetic properties.
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