EFFECTS OF ETIDRONATE AND OOPHORECTOMY ON THE ZETA-POTENTIAL OF RAT BONE

Recent clinical trials in osteoporotic patients show that cyclical eti dronate therapy can increase vertebral bone mass and reduce the incide nce of vertebral fractures, Stress generated potentials, which are the orized to participate in a negative feedback arrangement regulating bo ne and which are electrokinetic in origin, can be characterized in vit ro by the zeta potential, a measure of electrical surface charge, Thus , the possible effects of etidronate and oophorectomy on the zeta pote ntial of bone were investigated with respect to bone remodeling, patho physiology, and osteoporosis. Thirty-two oophorectomized and 48 sham o ophorectomized rats received subcutaneous etidronate or saline, The ze ta potential magnitude of the control group (sham oophorectomized, veh icle only) increased 23.6% from age 6 to 10 months, a period of bone g rowth, After 6 weeks of etidronate treatment, which decreased bone tur nover, the zeta potential magnitude was decreased 14.9% (0.59 mV) comp ared with that of controls, Decreased zeta potential magnitudes with e tidronate treatment also were observed in sham oophorectomized groups at 16 weeks and in oophorectomized groups at 6 and 16 weeks, but the d ifferences were not statistically significant, A large bolus of etidro nate had no effect, The zeta potential of bone is a dynamic quantity t hat may correlate with bone growth or bone turnover, Whether it exerts a causative effect or is a marker remains unknown.