IMAGE-ANALYSIS AND IMAGE-PROCESSING AS TOOLS TO MEASURE INITIAL RATESOF ENZYME-REACTIONS IN SECTIONS - DISTRIBUTION PATTERNS OF GLUTAMATE-DEHYDROGENASE ACTIVITY IN RAT-LIVER LOBULES

To analyze regional differences in the activity of glutamate dehydroge nase in rat liver in situ, we developed an image recording and process ing system for monitoring the formation of a colored final reaction pr oduct in time, All absorbance measurements of test and control reactio ns in time in consecutive sections were used to fit the data to a quad ratic curve, with the derivative at t = 0 representing the initial vel ocity of formazan formation, The images of sections incubated for test and control reactions were topographically matched with an affine tra nsformation using the positions of vessels as fiducials, Specific enzy me activity was calculated by subtracting the coefficients representin g the initial velocity at corresponding locations in the test and cont rol reactions and appeared to be 8 and 4 mu moles glutamate converted per min per cm(3) of tissue at 20 degrees C in pericentral and peripor tal zones of fasted female rats, respectively. Those values are in agr eement with biochemical data. The ability to construct two-dimensional images of cellular distribution patterns of enzyme activity in liver lobules is particularly useful for the study of metabolic zonation in this organ.