Metabolic heterogeneity among human monocytes and its modulation by PGE2.

Abstract Human peripheral blood monocytes (Μø) were fractionated on a discontinuous bovine serum albumin density gradient, and cells from each fraction was assayed for their specific activity of two enzymes, which represent correlates of Μø activation or differentiation (5’-nucleotidase, acid phosphatase) and their synthesis of prostaglandin E2 (PGE2). On the basis of significant differences in these parameters, the monocytes could be divided into two broad populations. Low density cells demonstrated low specific activities of 5’-nucleotidase (5’N), high specific activities of acid phosphatase (APT’ase), and synthesized substantial amounts of PGE2. In contrast, 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 Μø subpopulations, low and high density Μø 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 Μø, differences in 5’-N and APT’ase remained as useful discriminators of the Μø subpopulations. The pertinence of these findings to events involved in Μø activation and differentiation as well as a possible role for PGE2 in modulating these events is discussed.