OVARIECTOMY CAUSES CELL-PROLIFERATION AND MATRIX SYNTHESIS IN THE GROWTH-PLATE CARTILAGE OF THE ADULT-RAT

The in vivo effects of ovariectomy in rats have been studied on cell p roliferation and matrix synthesis in the growth plate cartilage by ass essing immunohistochemically the levels of proliferating cell nuclear antigen and chondroitin sulphate proteoglycan(s). The serum levels of insulin-like growth factor-I and growth hormone were also measured by radioimmunoassay procedures. At 5 weeks after ovariectomy, the serum l evels of the growth factor were significantly higher than those in sha m-operated rats. in contrast, the level of growth hormone was lower. T he nuclear staining of proliferating cell nuclear antigen was generall y seen in the zone of proliferative chondrocytes from both groups of r ats. Whereas almost all chondrocytes in the proliferative zone of ovar iectomized rats expressed proliferating cell nuclear antigen immunorea ctivity, fewer did so in that of the sham rats. Quantitative image ana lysis by ACAS 570 laser cytometry demonstrated that the nuclear antige n-positive sites in ovariectomized rats had significantly higher integ rated values (staining intensity), areas and perimeters than those in sham rats. In addition, the number of chondroitin sulphate proteoglyca n-immunoreactive cells in the proliferative chondrocytes was also high er in ovariectomized rats than in sham ones. These results suggest tha t ovariectomy significantly stimulates the cell proliferation and matr ix synthesis in the growth plate cartilage, probably through the highe r serum level of insulin-like growth factor-I. (C) 1998 Chapman & Hall .