DISTRIBUTION OF ECTO-5'-NUCLEOTIDASE IN THE RAT-LIVER - EFFECT OF ANEMIA

In the kidney a striking parallel exists between the expression of ect o-5'-nucleotidase and of erythropoietin by renal fibroblasts. It was t herefore hypothesized that the expression of ecto-5'-nucleotidase in f ibroblasts might be controlled by oxygen tension. In order to test thi s hypothesis, we examined the distribution of the enzyme in a tissue w hich displays a defined zonation in respect to oxygen tension, namely in the liver; anaemia was used in order to exaggerate this zonation. T he distribution of ecto-5'-nucleotidase was investigated by light and electron microscopy using enzyme and immunohistochemical methods in th e livers of healthy and of anaemic rats. Anaemia was produced by haemo lysis combined with X-ray irradiation. The enzyme was detected in the bile canaliculi, in the connective tissue of the portal triads and of the central veins, and in fat-storing cells probably corresponding to a special form of fibroblasts. In healthy animals the perisinusoidal e cto-5'-nucleotidase activity was slightly higher in the pericentral th an in the periportal area of the acinus whereas the inverse was observ ed for the staining of bile canaliculi. Anaemia provoked an increase o f ecto-5'-nucleotidase in fat-storing cells in the pericentral zone of the acinus and in fibroblasts around the central veins, resulting in steepended gradients along the sinusoids. The intralobular gradient of ecto-5'-nucleotidase in perisinusoidal cells and the effect thereon o f anaemia suggest that the expression of the ecto-5'-nucleotidase migh t be directly or indirectly controlled by local oxygen tension.