Removal of extracellular fluid from muscle: assessment of a method.

Controlled compression of mouse biceps brachii muscle caused only partial extrusion of an extracellular protein (125I-albumin) from the muscle. Concentrations of sodium and potassium in the expressed fluid at any stage of compression did not correspond with concentrations expected for extracellular fluid. This procedure, therefore, does not selectively remove extracellular fluid from muscle.