ENDOGENOUS PEROXIDASE IN THE NUCLEAR-ENVELOPE AND ENDOPLASMIC-RETICULUM OF HUMAN-MONOCYTES INVITRO - ASSOCIATION WITH ARACHIDONIC-ACID METABOLISM

The development of peroxidase (PO) reaction in the nuclear envelope (NE) and endoplasmic reticulum (ER) of monocytes differentiating in vitro and its relationship with arachidonic acid metabolism were studied. The PO, as visualized by the diaminobenzidine (DAB) technique, appeared in the NE and ER of the majority of monocytes within 24 h of culture, with a substantial decrease thereafter. The influence of 3 major groups of agents, inhibitors of PO, of prostanoids, and of protein biosynthesis on the development of the PO reaction was examined. When aminotriazole, a PO inhibitor, was added to the culture medium, the appearance of PO was suppressed in the monocytes. The cyclooxygenase blocker, indomethacin did not influence the development of PO. Also the blockers of protein synthesis, puromycin, cycloheximide and actinomycin D, did not affect the appearance of PO. The prostanoids released from the monocytes, i.e., prostaglandin E and thromboxane B2, were determined by radioimmunoassay and showed a time sequence of secretion that corresponded to the appearance of PO in the cells; a marked increase within the first 24 h with a substantial decrease thereafter. The presence of the PO inhibitors aminotriazole and sodium azide in the culture medium produced a suppression of prostanoid release from the monocytes comparable with that of indomethacin. The PO in the NE and ER of differentiating monocytes in vitro is associated with arachidonic acid metabolism, and is not formed by de novo protein synthesis but rather by an activation process.