DISPLACEMENT OF ACID-PHOSPHATASE AND ALKALINE-PHOSPHATASE PROTEINS INTHE RAT-KIDNEY DURING A DEHYDRATION PROCEDURE - AN ADVANTAGE OF ULTRATHIN FROZEN-SECTIONS FOR DETECTING PRECISE LOCALIZATION OF AN ENZYME-ACTIVITY

The localizations of acid phosphatase and alkaline phosphatase activit ies were observed in Epon ultrathin sections of rat kidneys which had been either fixed with 2% glutaraldehyde or 4% paraformaldehyde, or fi xed and then dehydrated by ethanol or acetone, and in ultrathin frozen sections of 2% glutaraldehyde fixed specimens. Prior to dehydration, acid phosphatase activity was positive in lysosomes, and alkaline phos phatase activity on the luminal side of brush border membrane. In the kidneys which had been fixed then dehydrated with ethanol, acid phosph atase activity was observed in the cytoplasm near lysosomes and on the plasma membrane, as well as in lysosomes, and alkaline phosphatase ac tivity in the cytoplasm and on the cytosolic side of the brush border. These results seem to indicate the displacement of enzyme proteins du ring a dehydration procedure. On the other hand, acid phosphatase acti vity was clearly localized in lysosomes, and alkaline phosphatase acti vity on the luminal side of the brush border membrane on the ultrathin frozen sections of rat kidneys which were fixed with 2% glutaraldehyd e. The ultrathin frozen sections had not been exposed to organic solve nts prior to demonstration of enzyme activities. The present study sho ws that an ultrathin frozen section is the most suitable for demonstra ting enzyme activities directly on an ultrathin section.