Alterations in bone marrow leukocyte ultrastructure and alkaline phosphatase activity accompanying a peripheral inflammatory response in the rat (Abstract)

Abstract

The alterations in leukocyte counts in peripheral blood which occur during a local inflammatory response are accompanied by changes in both mitotic activity and ultrastructural morphology of bone marrow precursors. In unstimulated marrow from young adult male Sprague-Dawley rats, alkaline phosphatase (AP) activity, as demonstrated by an osmiophilic method (Williams et al, 1979 J. Histochem. Cytochem. 27, 665) is evident on the plasma membrane of eosinophils from the late promyelocyte stage onwards. Neutrophils are much less heavily labelled, the enzyme not being demonstrable until the metamyelocyte stage. Within 30 min of the subcutaneous injection of turpentine (4 ml/kg body weight) depletion of mature netrophils is apparent, becoming marked by 12 h. To compensate for this depletion, mitotic activity increases significantly after 12 h, involving all stages from the myeloblast, which is rarely seen dividing in resting marrow, to myelocyte. Additionally AP activity becomes evident in myeloblasts and promyelocytes. At 12h dividing neutrophil precursors dominate the bone marrow, and although eosinophil numbers remain unchanged, they frequently fail to exhibit AP activity. By 20h, as a consequence of earlier mitotic activity, numerous mature neutrophils are seen, many exhibiting AP activity, but mitotic activity appears less marked.