Evaluation of testing solution and storage for measuring passive elastic modulus of rat tibialis anterior whole...

Ex-vivo tensile testing is widely used to evaluate the passive mechanical properties of skeletal muscle, particularly the elastic modulus. Researchers commonly use different testing solutions, such as relaxing and carbogen-bubbled Tyrode, and often store small samples in glycerinated solution prior to testing. This paper investigated the effects of testing solutions and storage conditions on the passive elastic modulus of whole muscles in three studies. The objectives were to compare the elastic modulus of whole muscles tested in relaxing solution, Tyrode's solution, and carbogen-bubbled Tyrode's solution (Studies A&B) and to determine whether storage methods can preserve muscles' passive mechanical properties (Study C). Tibialis Anterior muscles (left and right) from 28 male Sprague-Dawley rats were harvested. In Study A, six rats were studied to compare the effect of using relaxing and Tyrode's solutions. Study B involved muscles from eight rats to assess the impact of carbogen aeration in Tyrode's solution. In Study C, 14 rats were used to evaluate the effects of storing muscles in glycerinated solution compared to fresh muscles using three different methods with varying storage durations. The results indicated no significant differences in elastic moduli between relaxing and Tyrode's solutions (p = 0.70) or between carbogen bubbled and non-bubbled Tyrode's solutions (p = 0.81). Also, none of the storage methods preserved the passive elastic modulus of whole muscles compared to fresh muscles, highlighting the need for new storage methodologies if storing whole muscle is required prior to testing. These findings improve the interpretation of passive mechanical property measurements across studies with different conditions.