AJP - Gastrointestinal and Liver Physiology, Vol 272, Issue 4 698-G704, Copyright © 1997 by American Physiological Society
A unique myosin isoform transition in cat striated external anal sphincter muscle induced by denervation
R. Kustasz, W. Helferich, T. Adams and J. Krier
Department of Physiology, Michigan State University, East Lansing 48824-1101, USA.
Denervation of limb and trunk muscles leads to characteristic changes in
their biochemical properties. However, the effects of denervation of the
striated external anal sphincter (EAS) muscle have not been studied, even
though denervation is a common etiology for fecal incontinence. The present
study reports effects ofdenervation of the cat EAS and compares them with
changes in a denervated limb muscle [cat extensor digitorum longus (EDL)].
Nerves supplying the EAS and the EDL were sectioned in anesthetized cats,
which were allowed to recover and live for 10, 30, or 60 days. Their
muscles were then excised, and myofibrillar proteins were isolated. Myosin
heavy chain (MHC) isoform composition was measured by sodium dodecyl
sulfate-polyacrylamide gel electrophoresis. The EDL and EAS showed
progressive increases in MHC type IIA and progressive decreases in MHC type
IIB at 10, 30, and 60 days. MHC type I progressively increased in the EDL
but showed no change in the EAS. We hypothesize that this distinctive
transition is related to the unique embryological origin and function of
the EAS.
