X-ray microanalysis of cartilage and chondrocytes.

The elemental content of differentiating chondrocytes in situ and in vitro was studied by X-ray microanalysis. The in situ studies were carried out on semi-thick cryosections and on thin sections of freeze-dried low-temperature vacuum-embedded rat rib growth plate. Resting, proliferative, and hypertrophic cells were analyzed separately. The in vitro studies were carried out on cultured cell fractions isolated from rat rib growth plate. The cell fractions were relatively homogeneous and contained resting - early proliferative, proliferative or hypertrophic cells, respectively. Data from cells in vitro are generally not comparable to data obtained from cells in situ. Chondrocytes in situ contain relatively high levels of Na, which is probably due to: (1) high Na levels in the cartilage matrix formed intracellularly, and (2) low supply of oxygen and nutrients. High Na levels in (some of) the proliferative cells may also be related to mitotic activity. The chondrocyte matrix contains relatively high levels of K. The data in the present study are compared to those of previous studies on the elemental content of chondrocytes.