Androgen metabolism by human peritoneal macrophages
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C C Coddington1, G S Letterie, T A Klein
1Department of Obstetrics and Gynecology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814.
Abstract:
Peritoneal macrophages (PM) were obtained by peritoneal dialysis from a regularly menstruating woman with renal failure. Macrophages (10(6) cells) were incubated at 37 degrees C for various periods of time (0-4 hr) in the presence of 14C-androstenedione or 3H-androstenedione and various concentrations (0.06-5.06 microM) of nonradiolabeled androstenedione (A). Testosterone (T) formed was purified by column chromatography, thin layer chromatography, acetylation, and recrystalization to constant 3H:14C ratios. The rate of formation of T from A was linear for nearly 2 hr. Conversion of A to T was linear at cell numbers in the incubation up to 1 x 10(6). The formation of T from A followed Michaelis-Menten kinetics at concentrations of A between 0.06 and 5.06 microM. The apparent Km of the enzyme for A was 0.75 microM and the Vmax for T formation from A in these cells was 33.9 pmol x hr-1 x 10(6) cells-1. PM were obtained also from normal patients (n = 6) and patients with endometriosis (n = 5). The rate of T synthesis from A in PM obtained from patients with endometriosis [527 +/- 263 pmol x hr-1 x 10(6) cells-1 (mean +/- SEM, n = 5)] was similar to that observed in PM obtained from normal patients [518 +/- 226 pmol x hr-1 x 10(6) cells-1 (mean +/- SEM, n = 6)]. We observed a near 30-fold variation in the rate of formation of T from A by PM obtained from different individuals (range 54 to 1580 pmol x hr-1 x 10(6) cells-1). Further study is needed to elucidate the physiologic significance of PM androgen metabolism and its relationship to reproductive function.
Insights
Peritoneal macrophages convert androstenedione to testosterone. This androgen metabolism in macrophages shows significant individual variation but is similar between normal and endometriosis patients.
Area of Science:
- Reproductive Endocrinology
- Cellular Metabolism
- Immunology
Background:
- Peritoneal macrophages (PM) are immune cells present in the peritoneal cavity.
- Androgen metabolism plays a crucial role in reproductive health.
- The metabolic activity of macrophages in relation to reproductive hormones is not fully understood.
Purpose of the Study:
- To investigate the conversion of androstenedione to testosterone by human peritoneal macrophages.
- To characterize the kinetics of this enzymatic conversion.
- To compare the androgen metabolism in PM from normal individuals and patients with endometriosis.
Main Methods:
- Peritoneal macrophages were isolated from a woman with renal failure and healthy/endometriosis patients.
- Macrophages were incubated with radiolabeled androstenedione (A) and varying concentrations of non-labeled A.
- Testosterone (T) formation was quantified after rigorous purification and kinetic analysis (Michaelis-Menten kinetics).
Main Results:
- Peritoneal macrophages efficiently convert androstenedione to testosterone.
- The conversion followed Michaelis-Menten kinetics with an apparent Km of 0.75 microM and Vmax of 33.9 pmol x hr-1 x 10(6) cells-1.
- Rates of testosterone synthesis from androstenedione were comparable between normal (518 +/- 226) and endometriosis (527 +/- 263) patient PM, but showed a ~30-fold inter-individual variation (54-1580 pmol x hr-1 x 10(6) cells-1).
Conclusions:
- Human peritoneal macrophages possess the enzymatic capacity to metabolize androgens.
- The rate of androstenedione to testosterone conversion by PM exhibits substantial inter-individual variability.
- Further research is warranted to clarify the physiological significance of PM androgen metabolism in reproductive function.