Transient and cyclic responses of strain-generated potential in rabbit patellar tendon are frequency and pH dependent

The goal of this study was to expand understanding of strain-generated pote ntial (SGP) in ligamentous or tendinous tissues. Most SGP studies in the pa st have focused on cartilage or bone. Herein, rabbit patellar tendon (PT) w as used as a model. Each patellar tendon had two Ag/AgCl electrodes inserte d at axial positions of 1/4 and 1/2 from patellar to tibial insertions. Eac h specimen was electrically isolated, gripped iii a servohydraulic test sys tem, and then subjected to a short session of uniaxial haversine tension (2 .5 percent maximum strain) at a frequency of 0.5, 1.0, 2.0, or 5.0 Hz. A cy clic (sinusoidal) electrical potential superimposed upon a larger transient (exponentially asymptotic) potential was consistently observed Upon termin ation of loading, the cyclic SGP ended, and the shifted baseline of the SGP exponentially decayed and asymptotically returned to a residual potential which over all specimens was not different than the original potential. The transient and cyclic SGPs were frequency dependent (P<0.001, P=0.06, respe ctively). To our knowledge, this transient portion of the SGF, although the oretically predicted by Suh (1996, Biorheology, 33, pp. 289-304) and Chen ( 1996, Ph.D. thesis, University of Wisconsin-Madison) has not been observed in other experiments using different protocols. Additional PTs were dehydra ted and the rehydrated in solution at different pH levels. The magnitude of SGPs increased in basic solution (pH 9.5) but diminished in pH 4.7 buffer. This pH dependency suggests that electrokinetics is the dominant mechanism for the transient and cyclic responses of the SGPs, although this study do es not provide direct evidence. [S0148-0731(00)00105-9].