title: B lymphopoiesis is upregulated after orchiectomy and is correlated with estradiol but not testosterone serum levels in aged male rats.
abstract: Previous studies have shown that B lymphopoiesis is augmented after androgen withdrawal in male mice. As an analogy to the skeletal system, some effects of androgens on the proliferation of B cells may be mediated via aromatization into estrogens in vivo. The aim of the present study was to assess the effects of androgen withdrawal on B lymphopoiesis in bone marrow of aged male rats sequentially over a period of 9 months, and to correlate the flow-cytometric findings with changes in systemic levels of sex steroids. We first showed that androgen withdrawal is associated with enhanced B lymphopoiesis in bone marrow of 4-month-old male orchiectomized (ORX) rats, and that the changes in the bone marrow B cell compartment in ORX animals can be reversed by testosterone supplementation. In a subsequent, sequential experiment, we found that orchiectomy induced a sustained rise in Thy 1.1+/CD45R+ bone marrow cells committed for the B cell lineage that lasted for several months in 13-month-old aged rats. In a stepwise model of multiple regression analysis using estradiol, free and total testosterone as independent variables, estradiol was the strongest predictor of the percentage of B precursor cells in bone marrow in aged SHAM and ORX rats. Free and total testosterone did not correlate with B lymphopoiesis in aged SHAM rats. The current experiment has clearly shown that androgen withdrawal upregulates the number of B lineage cells over several months in rat bone marrow. Furthermore, our results provide evidence that estradiol may play an important role as a physiological suppressor of B lymphopoiesis in aged male rats.
authors.affiliation: Institute of Physiology, Physiological Chemistry and Animal Nutrition, Ludwig Maximilians University, Munich, Germany. R.Erben@lrz.uni-muenchen.de
authors.forename: R G
authors.initials: RG
authors.lastname: Erben
authors.forename: J
authors.initials: J
authors.lastname: Eberle
authors.forename: M
authors.initials: M
authors.lastname: Stangassinger
mesh_terms: D000375:Aging / Q000378:metabolism*; D000728:Androgens / Q000378:metabolism; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D004958:Estradiol / Q000097:blood*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006410:Hematopoiesis / Q000187:drug effects / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D008297:Male; D009919:Orchiectomy; D051381:Rats; D011916:Rats, Inbred F344; D012044:Regression Analysis; D013739:Testosterone / Q000097:blood / Q000494:pharmacology; D015854:Up-Regulation / Q000502:physiology
chemical_list: D000728:Androgens; D013739:Testosterone; D004958:Estradiol