Effect of malnutrition and primiparity on the pubococcygeus muscle of the rat.

It is well known that chronic malnutrition affects the structure and function of skeletal muscles, particularly those involved in joint movement. However, there is no evidence of the effect of dietary restriction on muscles of the pelvic area involved in urination and parturition. In this work we aimed to analyze the effect of primiparity and malnutrition on the composition of the different types of fibers in the pubococcygeus muscle (mPc) of the rat. We used mPc from 4 groups of Wistar rats: control (C), malnourished (D), primiparous control (PC) and primiparous malnourished (PD), which were serially cut (10m) and stained with ATPase and NADH histochemical techniques. Subsequently, microphotographs were taken, fiber types were identified by their tonality and relative percentages were determined. The results obtained show that malnutrition and/or primiparity do not cause significant changes in the percentage of oxidative and slow fibers in the mPc, but do increase the percentage of intermediate fibers, with predominance of glycolytic metabolism (between 9 and 5%, respectively), concomitant with a reduction in the percentage of glycolytic fast fibers. Our results suggest that by parturition and malnutrition a compensatory effect is established that induces the transformation of fast to intermediate fibers in the pelvic muscles of the rat.Study partially supported by: CONACyT 265483 postdoctoral fellowship to KLG, SNI to ERT, KLG and IJE, PROMEP-1006 grant to ERT, Sofia Kovalévskaya Award to ER.