Solute concentration gradients in frog muscles at 0 degree C: active transport or adsorption?

In isolated frog muscle that has been incubated for 7 days at 0 degrees C invitro K(+) and Na(+) remain at normal concentrations. Amino acids are accumulated against a concentration gradient at this temperature; for example, glycine accumulates in muscle to a concentration ten times that in the external solution. The amount of cycloleucine accumulated is greater at 0 degrees C than at 25 degrees C. These findings, which are difficult to explain on the basis of metabolically linked active transport, are Consiststent with the view that solute accumulation by cell is the result of adsorption on spesific sites.