Fiber type characterization of striated muscles related to micturition in female rabbits

Fiber type composition of pubococcygeus and bulbospongiosus striated muscles is modified by multiparity in the rabbit

“…This is supported by the observations reported by Fajardo and collaborators (2008), which found a significative reduction in the contractile force developed by the Pc muscle during a single twitch or tetanus . The proper contractile function of the Pc muscle and activation during the micturition process could require a relative proportion of a particular type of muscle fibers with predominance of oxidative metabolism, which changes after multiparity. The loss of such oxidative predominant metabolism after multiparity may thus be linked to episodes of urine dropping during the induced micturition …”

“…Tissue sampling and preparation. Pc and Bs muscles were dissected under anesthesia as described elsewhere . A midline incision was made from the abdomen to the perineal vagina, and abdominal muscles and adipose tissue were removed to harvest Bs muscles.…”

“…For each muscle, the cross sectional area (CSA) was measured in 100 randomly selected fibers of each fiber type stained with NADH‐TR and alkaline ATPase using the AxioVision Rel 4.3 program (Carl Zeiss, Germany). Changes in fiber type composition in muscles were determined by comparing the raw data obtained in multiparous rabbits obtained in this series of experiments with those obtained from nulliparous female reported elsewhere . In addition, the percentage of intermediate fibers with predominance of oxidative or glycolytic metabolism was inferred from the averaged percentage of oxidative fibers minus the averaged percentage of slow fibers (% Intermediate‐oxidative = % oxidative (NADH‐TR) − % slow fibers (alkaline ATPase) ) and from the percentage value of glycolytic fibers minus the percentage value of fast fibers (% Intermediate/glycolytic = % glycolytic (NADH‐TR) − % fast fibers (alkaline ATPase) ), respectively.…”

“…Most of the observed effects could be explained, among other factors, by changes in the proportion of fiber type phenotypes in each muscle. Fiber type composition of the Pc muscle comprises a heterogeneous proportion of slow‐oxidative (type I), fast oxidative‐glycolytic (type IIa/d), and fast glycolytic fibers (type IIb), while the Bs muscle is predominantly composed by fast glycolytic fibers …”

“…To accomplish this, we use the alkaline ATPase (9.4 pH) and NADH‐TR histochemical techniques in order to characterize the fibers according to their ATPase enzyme activity and the predominant metabolism (glycolytic or oxidative) present in them. Data from nulliparous female rabbits were reported in a previous study and in this study they are used to establish the probable changes in the relative proportion of fiber types in muscles of multiparous rabbits.…”