抄録
The intracellular distribution of angiotensin I-converting enzyme (ACE) in sarcoid lymph nodes was examined to find out the mechanism of the elevation of serum ACE in sarcoidosis patients. Cell fractionation of sarcoid lymph nodes and normal human lung was performed. Tissue was homogenized with 0.25M succurose-phosphate buffer, and 78000×g centrifugation was performed for 90min. The supernatant of this step was described as the soluble fraction. The precipitate of this step was treated with trypsin to solubilize membrane-bound enzyme, and solubilized enzyme by this step was described as the membrane-bound enzyme. In sarcoid lymph nodes, 73% of the total ACE was found in the soluble fraction. This was in contrast to normal lung in which more than 75% of the activity was found in the membrane fraction. Characteristics such as optimal pH, molecular weight, inhibition by bradykinin ptentiating peptide and Km, of enzymes from normal serum, serum of a sarcoidosis patient, normal human lung, soluble fraction of sarcoid lymph nodes and membrane-bound enzyme of sarcoid lymph nodes were identical to each other except for the effect of temperatures. The enzyme from the soluble fraction in sarcoid lymph nodes was less stable than that from the membrane fraction at 50°C and 53°C and was similar to that in serum. It was suspected that the enzyme in sarcoid lymph node is easily liberated to the blood stream and causes the elevation of serum ACE in sarcoidosis patients.
