Metabolic heterogeneity among human monocytes and its modulation by PGE2.

Abstract

Human peripheral blood monocytes (M.vphi.) were fractionated on a discontinuous bovine serum albumin density gradient, and cells from each fraction was assayed for their specific activity of 2 enzymes, which represent correlates of M.vphi. activation or differentiation (5''-nucleotidase, acid phosphatase) and their synthesis of prostaglandin(PG)E2. On the basis of significant differences in these parameters, the monocytes could be divided into 2 broad populations. Low density cells demonstrated low specific activities of 5''-nucleotidase (5''N), high specific activities of acid phosphatase (ATP''ase), and synthesized substantial amounts of PGE2. High density cells demonstrated high specific activities of 5''-N, low specific activities of APT''ase and synthesized meager amounts of PGE2. To determine if these biochemical differences served as stable markers of M.vphi. subpopulations, low and high density M.vphi. were individually cultured for 3 days, and changes in the metabolic parameters were assayed. Although 5''-N and APT''ase increased among each population, the magnitude of this change could be modulated by PGE2. When each population was cultured in a concentration of PGE2 equivalent to that synthesized by the whole M.vphi., differences in 5''-N and ATP''ase remained as useful discriminations of the M.vphi. subpopulations. The pertinence of these findings of events involved in M.vphi. activation and differentiation as well as a possible role for PGE2 in modulating these events is discussed.