A comparison of the mechanical properties of oesophageal striated muscle with skeletal muscles of the guinea pig.

An in vitro comparative study has been made of the contractile properties of guinea pig oesophageal striated muscle with fast twitch (extensor digitorum longus) and slow twitch (soleus) muscles. Histochemical analysis of sections showed oesophageal fibres to react in a manner typical of fast twitch muscles. Isometric measurements made at 23 and 37 degrees C indicated that oesophageal striated muscle contracts at speeds similar to, but still significantly faster than soleus. Isotonic measurements of oesophageal preparations made at 23 degrees C gave an intrinsic speed of shortening and an a/Po value derived from Hill's equation, comparable with that obtained for soleus. The reason for the contradiction between the results from histochemistry, and the results from isometric and isotonic contractions are not apparent, but may be due to differences in fibre arrangement between oesophagus and the two skeletal muscles.