Stereological Study of the External Urethral Sphincter in the Female Urethra of the Lamb: A New Model for Studies on Urinary Continence

Abstract

Some of the morphometrical features and functional properties of the lamb external urethral sphincter (EUS) were determined by means of ATPase histochemistry. In this study, eight female urethras of 2- to 3-month-old lambs were used. The samples were studied by using an unbiased stereological design and were statistically evaluated with a Kolmogorov-Smirnov test. Additionally, the mechanical activity of the different fibre types was analysed by measuring the isometric changes in tension induced by electrical field stimulation (EFS) of intrinsic nerves. The lamb EUS has an average fibre density of 1142.37 fibres/mm(2) (SD = 279.33). Our data showed the predominance of fast-twitch fibres or type II fibres, with a proportion of 30% (type I) and 70% (type II) in all cases. These percentages remained the same along the length of the EUS. However, a clear tendency to increase the number of both fibre types in the mid-EUS was observed. Interestingly, type I and II fibres are intermingled throughout the whole lamb EUS. Dynamic parameters of the contraction induced in lamb EUS preparations by EFS of intramural nerves, were intermediate between fast- and slow-twitch muscles. Furthermore, contractile activity showed no decrease in amplitude upon repetitive stimulation, suggesting the presence of a mixture of fibre types, in which fast but fatigue-resistant fibres (probably type IIA) seem to predominate. Our results indicate that lambs could be suggested as a new biological model to study those pathological processes, which involve the sphincteric regulation of the EUS.

The Anatomy of Caprine Female Urethra and Characteristics of Muscle and Bone Marrow Derived Caprine Cells for Autologous Cell Therapy Testing

“…B). This observation is consistent with a previously published description of EUS in lambs (Rodriguez‐Veiga et al, ). Our data show that a short vestibular part of EUS is present in goats as it ends in the vestibular wall few millimeters caudally from the external urethral orifice.…”

Anatomic and functional properties of bulboglandularis striated muscle support its contribution as sphincter in female rabbit micturition

“…There is a great variability in given names for the urethral striated musculature possibly due to particular morphological differences between mammal species . For example, urethral sphincter in female rats is composed of striated fibers surrounding urethra that are closely associated with this viscera .…”

“…There is a great variability in given names for the urethral striated musculature possibly due to particular morphological differences between mammal species. 10,[19][20][21] For example, urethral sphincter in female rats is composed of striated fibers surrounding urethra that are closely associated with this viscera. 10 The SUS in women has three portions, the compressor urethrae and urethrovaginal sphincter covering the urethra and vagina; 2 and the urethral rhabdosphincter surrounding the urethra.…”

Sexual and Regional Differences in Myosin Heavy Chain Expression in the Rat External Urethral Sphincter

“…An in‐depth knowledge of the fiber‐type composition of the EUS is essential to evaluate its functional and metabolic properties. Both early and more recent enzyme‐based and immunohistochemical analyses have demonstrated the composition of the fiber types in the EUS of different species and in both sexes of animals, including human beings (Gosling et al, ; Schrøder and Reske‐Nielsen, ; Tokunaka et al, ; Sautet et al, ; Tokunaka et al, ; Praud et al, ; Rodrígues‐Veiga et al, ; Biérinx and Sebille, ; Buffini et al, ; Chen et al, ). Immunostaining for fast and slow myosin heavy chain (MHC) isoforms has shown that the female rat EUS contains mainly Type 2 (fast) and Type 1 (slow) fibers (Praud et al, ).…”