An autoradiographic study of H 3-proline utilization by aging mouse skeletal tissues—II. Cartilage cell compartments

Abstract

In an autoradiographic study the uptake, turnover and distribution of H 3-proline was assessed at the femoral epiphyseal plate and articular cartilage of 5 to 52 weeks old mice. Ninety-nine shortlived BNL mice were given H 3-proline in a single dose of 2 μCi/gm body weight (Sp. Act. = 1 Ci/mM) and killed between 15 min to 14 days later. NTB-3 autoradiograms which were exposed for 16 days were prepared and stained with hematoxylin. Grain counts were made over epiphyseal and articular cartilage cell compartments and the data statistically evaluated. The results showed significant uptake and utilization of H 3-proline by both cell types, although the activity of epiphyseal cartilage was initially higher. H 3-proline was utilized extensively for matrical precursor formation, as well as, for a variety of intracellular substances necessary for cellular viability. The uptake and turnover of H 3-proline was diminished in both cell compartments by 26 weeks of age, revealing peak activity shifts. At 52 weeks the uptake by epiphyseal cartilage cells was insignificant, whereas, articular cartilage activity was retained. The significantly diminished grain counts observed over epiphyseal plate cells with increasing age, reflect release of physiological demands for matrical precursor formation, closure of the plates and termination of longitudinal growth. The continued significant H 3-proline uptake exhibited by articular cartilage was a reflection of the physiological requirement for maintenance of normal joint function throughout the life-span of the organism. The maintenance of cell viability against accumulating age changes is essential to the integrity of the articular cartilage.