[Chromatin activation as affected by lysosomal proteinases using fluorescent probes]

Activation of nuclear chromatin from rat liver tissue was studied using acridine orange fluorescent probes after partial hepatectomy of after intensive physical exercises in vivo. Under the both conditions the restoration period was characterized by an increase in protein-synthesizing and proliferative reactions, involving preactivation of the lysosomal apparatus in hepatocytes, translocation of lysosomes and association of lysosomal enzymes with nuclei. During the chromatin activation binding of DNA with acridine orange was increased. Vinblastine, administered intraperitoneally at a dose of O.1 mg/100 g during the operation or 1 hr before the exercises, which is recognized as an inhibitor of lysosome translocation, as well as hordox (2,500 un/100 g), an inhibitor of proteinases, decreased distinctly the DNA affinity to acridine orange in both groups the animals studied. In vitro activation of chromatin occurred after incubation of liver nuclei, isolated from intact rats, with the fraction of liver lysosomes. In this case amount of binding sites was increased in DNA by 175%. Pretreatment of lysosomes with EDTA did not affect the chromatin activation. Soy bean inhibitor and iodacetamide decreased the amount of binding sites in chromatin by 115%. Pepstatine decreased completely the activating effect of lysosomes. Thus, three types of lysosomal enzymes: carboxypeptidases, serine- and thiol-dependent proteinases participated in activation of chromatin after the contact of lysosomes with nuclei.