A comparison between the physiological and histochemical characterisation of urethral striated muscle in the guinea pig
Whitmore, I.; Gosling, J.A.; Gilpin, S.A.
Pflugers Archiv European Journal of Physiology 400(1): 40-43
1984
ISSN/ISBN: 0031-6768 PMID: 6231526 Document Number: 226930
In an in vitro study a comparison was made between the actomyosin ATPase activity and the contractile properties of the external urethral sphincter in the guinea pig. Histochemical analysis showed the external urethral sphincter to contain a mixture of alkali and acid stable actomyosin ATPase positive fibers in the ratio of 3:1. External urethral sphincter isometric contraction measurements were undertaken using specimens mounted transversely or longitudinally with respect to the urethral lumen. These contraction parameters showed that the majority of fibers which constitute the external urethral sphincter correspond to the fast twitch type. To determine whether the relatively small fiber diameter of urethral striated muscle influenced the contraction results when compared with controls, corrections for different volume ratios of slow and fast fibers were applied to the results. These modified values revealed a close correlation between muscle fiber actomyosin ATPase content and isometric contraction responses.