IN-SITU MICRODIALYSIS IN BONE TISSUE - STIMULATION OF PROSTAGLANDIN E(2) RELEASE BY WEIGHT-BEARING MECHANICAL LOADING

In this study we describe, to our knowledge, the first experiment usin g the microdialysis technique for studying the release of prostaglandi n E(2) (PGE(2)) in the proximal tibia metaphysis secondary to mechanic al loading, Nine healthy females, six in the loading group and three c ontrols, mean age 34+/-2 (years+/-SEM), participated. A standard micro dialysis catheter was inserted into the tibia metaphyseal bone under l ocal anesthesia. Samplings were done every 15 min under a 2-h equilibr ation period, Thereafter, heel-drops (one impact per second) with as h ard impact of the heels into the floor as possible, were done for 5 mi n by the subjects in the loading group, The control group performed no exercise, Sampling continued after this for another 2-h period, Basal levels of PGE(2) in the proximal tibial metaphysis were determined to a mean of 45+/-10 pg/ml (mean+/-SEM, n = 6). The major finding was a 2.5-3.5-fold increase in the release of PGE(2) after mechanical loadin g. The increase was statistically significant (P < 0.05 compared with basal levels) 1 h after the mechanical loading and persisted for the r est of the experimental period, No major alterations were observed in the control group. In conclusion, our data demonstrate that in situ mi crodialysis is a useful method for studying the PGE(2) production in h uman bone, Furthermore, a rapid and significant increase in PGE(2) lev els was noticed in response to dynamic mechanical loading.