Extravascular localization of albumin and IgG in normal tonic and phasic muscles of the rat.

Interstitial space localizations of albumin and IgG by sensitive immunohistochemical methods have reaffirmed that many large molecular weight proteins exit the vascular system and pass into the interstitial spaces between skeletal muscle fibres. Extensor digitorum longus and soleus muscles were found to contain native albumin and IgG and perhaps other serum proteins such as complement C3 or fibrinogen. In addition, IgG content was observed to increase with age but both the locale and apparent concentrations of the other molecules remained unchanged.