The presence of
macroamylasemia can be suspected when a patient has low renal clearance of
amylase relative to
creatinine (Cam/Ccr). However, the Cam/Ccr is seldom reduced to the extent expected given the fraction of
amylase that appears to be bound in the
macroamylase complex by gel filtration studies at 3 degrees C. Therefore, we tested the possibility that the binding of
amylase in
macroamylase complexes was temperature dependent and that binding at physiological temperatures might be less than at 3 degrees C. Gel filtration of five
macroamylase-containing sera was carried out at temperatures of 3 degrees, 25 degrees, 37 degrees, 43 degrees, and 49 degrees C. Binding of
amylase in the complex decreased as the temperature increased with virtually all
amylase bound at 3 degrees C and virtually no
amylase bound at 49 degrees C. The fraction of the
amylase that bound at 37 degrees C was approximately what would have been predicted from the Cam/Ccr of each of the five subjects. We conclude that
amylase binding in
macroamylase complexes is extremely temperature sensitive and appreciable changes in binding may occur over the physiological temperature range of 37-41 degrees C.