Fiber type composition of pubococcygeus and bulbospongiosus striated muscles is modified by multiparity in the rabbit.
OBJECTIVE
We analyzed the effect of multiparity on the fiber type composition of two skeletal muscles involved in the maintenance of the micturition process, the pelvic pubococcygeus (Pc) and perineal bulbospongiosus (Bs) muscles in nulliparous and multiparous rabbits (Oryctolagus cuniculus).


METHODS
We used the basic ATPase and NADH-TR techniques to identify and characterize slow, intermediate, and fast fiber types and glycolitic and oxidative fibers in muscles, respectively.


RESULTS
Pc muscles of multiparous rabbits present relatively high percentages of slow and intermediate fibers but a low percentage of fast fibers (P < 0.05) as compared to Pc muscles from nulliparous rabbits, while percentages of glycolytic and oxidative fibers were similar (P > 0.05). Bs muscles of multiparous rabbits had a higher proportion of intermediate and glycolytic fibers (P < 0.05) than muscles of nulliparous. Both, Pc and Bs muscles of nulliparous and multiparous rabbits contain slow fibers with similar large cross sectional area, but fast fibers in multiparous muscles showed small cross sectional area than in nulliparous.


CONCLUSIONS
Multiparity modified the fiber type composition of Pc and Bs muscles in female rabbits. We propose that the contractile force and the physiological role of both muscles during micturition are affected because of the observed changes in the relative composition of muscle fiber types.
Departamento Fisiología, Biofísica y Neurociencias, Centro de Investigación y Estudios Avanzados Instituto Politécnico Nacional, México, Mexico.|Departamento de Biología Celular y Fisiología, Unidad Periférica Tlaxcala, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Tlaxcala, Mexico.
Kenia
K
López-García
Departamento Fisiología, Biofísica y Neurociencias, Centro de Investigación y Estudios Avanzados Instituto Politécnico Nacional, México, Mexico.
Silvia
S
Mariscal-Tovar
Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Tlaxcala, Mexico.
Martín Alejandro
MA
Serrano-Meneses
Departamento de Biología Celular y Fisiología, Unidad Periférica Tlaxcala, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Tlaxcala, Mexico.|Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Tlaxcala, Mexico.
Francisco
F
Castelán
Departamento de Biología Celular y Fisiología, Unidad Periférica Tlaxcala, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Tlaxcala, Mexico.|Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Tlaxcala, Mexico.
Margarita
M
Martínez-Gómez
Departamento Fisiología, Biofísica y Neurociencias, Centro de Investigación y Estudios Avanzados Instituto Politécnico Nacional, México, Mexico.
Ismael
I
Jiménez-Estrada
D000818:Animals; D005260:Female; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010298:Parity / Q000502:physiology*; D017773:Pelvic Floor / Q000502:physiology; D010502:Perineum / Q000502:physiology; D011247:Pregnancy; D011817:Rabbits; D014554:Urination / Q000502:physiology*
histochemistry; multiparity; muscle damage; pelvic floor; urinary incontinence