Effects of Etidronate and Oophorectomy on the Zeta... : Clinical Orthopaedics and Related Research® (original) (raw)

Research

Effects of Etidronate and Oophorectomy on the Zeta Potential of Rat Bone

Kowalchuk, Roman*,†; Corcoran, Thomas**; Pollack, Solomon*,**; Steinberg, Marvin**

From the *Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania.

**Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, Pennsylvania.

†Current affiliation: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania.

Supported in part by the National Institutes of Health Medical Scientist Training Program, the National Institutes of Health Special Center of Research Grant (5P50-AR39226-02), and the National Science Foundation (Grant 5-21367).

Reprint requests to Roman M. Kowalchuk, MD, PhD, Department of Radiology, Hospital of the University of Pennsylvania, 1 Silverstein Pavilion, 3400 Spruce St, Philadelphia, PA 19104.

Submitted: March 16, 1995.

Revised: September 5, 1995; October 17, 1995.

Accepted: October 18, 1995.

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Abstract

Recent clinical trials in osteoporotic patients show that cyclical etidronate therapy can increase vertebral bone mass and reduce the incidence of vertebral fractures. Stress generated potentials, which are theorized to participate in a negative feedback arrangement regulating bone and which are electrokinetic in origin, can be characterized in vitro by the zeta potential, a measure of electrical surface charge. Thus, the possible effects of etidronate and oophorectomy on the zeta potential of bone were investigated with respect to bone remodeling, pathophysiology, and osteoporosis. Thirty-two oophorectomized and 48 sham oophorectomized rats received subcutaneous etidronate or saline. The zeta potential magnitude of the control group (sham oophorectomized, vehicle only) increased 23.6% from age 6 to 10 months, a period of bone growth. After 6 weeks of etidronate treatment, which decreased bone turnover, the zeta potential magnitude was decreased 14.9% (0.59 mV) compared with that of controls. Decreased zeta potential magnitudes with etidronate treatment also were observed in sham oophorectomized groups at 16 weeks and in oophorectomized groups at 6 and 16 weeks, but the differences were not statistically significant. A large bolus of etidronate had no effect. The zeta potential of bone is a dynamic quantity that may correlate with bone growth or bone turnover. Whether it exerts a causative effect or is a marker remains unknown.

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