The following abstract presents results of a study conducted by a contract laboratory for the National Toxicology Program (NTP). The findings have not been peer reviewed and were not evaluated in accordance with the levels of evidence criteria established by the NTP on March 2009 (see http://ntp.niehs.nih.gov/ntp/htdocs/levels/09-3566%20NTP-ITOX-R1.pdf). The findings and conclusions for this study should not be construed to represent the views of the NTP or the US Government.
Immunotoxicity of Oxymetholone (CAS No. 434-07-1) in Male B6C3F1 Mice
NTP Report Number IMM90012
Oxymetholone is a synthetic androgen, structurally related to testosterone. Originally, it was used in the treatment of pituitary dwarfism and adjunctive therapy in osteoporosis. Its current use is limited to treatment of certain anemias. Anabolic steroids have been taken to improve strength and orally active anabolic steroids, such as oxymetholone, represent a class of abused drugs. Since sex steroids, including estrogen and testosterone, are well known to influence immune function at pharmacological or suprapharmacological levels the potential effects of oxymetholone on the immune system of mice were examined.
Oxymetholone was obtained from Sigma Chemical Corp. (Lot #037F0705) and was determined to be greater than 97% pure by HPLC. The material was prepared in saline containing 0.5% methylcellulose, and was administered daily for 14 consecutive days at doses of 50, 150, or 300 mg/kg by oral gavage in volumes of 0.2ml/10g body weight. Control mice received the vehicle and the positive control group received cyclophosphamide (Sigma Chemical Corp. Lot #67F-0155) by i.p. injection at daily doses of 25 mg/kg on days 11 through 14 of the study except in the host resistance tests where cyclophosphamide was administered at a single dose of 200mg/kg on day 14. Since oxymetholone is a synthetic androgen, male B6C3F1 mice, rather than female mice were used. On day 15, one day after the last exposure, the animals were evaluated for the indicated immunological and toxicological endpoints. Unless indicated, 7-8 mice were examined per treatment group for each endpoints.
General toxicological and immunological data are summarized in Table 1. There were no treatment-related effects on mortality, body weights or selected organ weights including spleen, thymus or liver (latter not shown). Hematological parameters were not remarkably affected, nor were serum chemistries (SGPT, glucose, total protein, albumin, globulin) although BUN levels were slightly elevated at the two higher doses. While bone marrow cell DNA synthesis in the 300 mg/kg treatment group was decreased, no effects were seen on cellularity or CFU-C2 progenitor cell formation (data not shown). There were no oxymetholone-related effects on the antibody response to sheep erythrocytes, natural killer cell activity, mitogenic responses to PHA, Con A or LPS, or the numbers of splenic T and B lymphocytes or T lymphcytes in subsets. The mixed leukocyte response was suppressed in the high- dose group and there was a slight decrease in the cytotoxic T lymphocyte response for all doses of oxymetholone. Macrophages, obtained from the peritoneal cavity of oxymetholone-treated mice, were equally responsive to activation by interferon-gamma as those from control mice when assessed by in vitro tumor cell killing (data not shown).
The ability of animals to resist infection with Listeria monocytogenes was not significantly compromised by oxymetholone treatment (Table 2).
Under these experimental conditions, the results suggest that treatment with oxymetholone can result in a mild decrease in cell-mediated immunity. However, when contrasted to the degree of suppression induced by cyclosphosphamide, and the limited alterations in other immune functions associated with oxymetholone exposure, the changes are considered minimal. The chemical treatment did not affect the ability of the animals to resist infection in the host resistance tests.
Table 1. Summary of Oxymetholone Immune Studies
|Body Weight (g)||28.6||28.2||27.8||28.6||28.1|
|Spleen:Body wt. (%)||0.48||0.41||0.50||0.55||0.26#|
|Thymus:Body wt. (%)||0.19||0.15||0.16||0.17||0.16|
|Spleen cell no. (x 10E7)||15.4||13.2||14.9||14.1||8.3#|
|Peripheral Leukocyte Count|
|Thy 1.2+ (%)||39.2||41.1||47.3||32.8||57.4*|
|Cytotoxic T Lymphocytes|
|(% cytotoxicity) 25:1||99.6||88.6*||87.5#||84.3#||83.0#|
|Natural Killer Cell Activity|
|(% cytotoxicity) 100:1||7.8||ND||9.3||9.2||ND|
|IgM PFC/spleen (x 10E3)||366||432||434||422||4#|
|Lymphoproliferation: 3H-TdR Incorporation (cpm x 10E3)|
|Mixed Leukocyte Response||47||34||45||29*||12#|
Abbreviation: CTX = cyclophosphamide;
* different from vehicle control at P less than 0.05
# different from vehicle control at P less than 0.01
ND = no data
Table 2: Summary of Oxymetholone Host Resistance Studies
|L. Monocytogenes||Dose (mg/kg/day)||CTX|
|Host Resistance Test||200mg/kg|
|(12 Per Group)||0||50||100||300|
|Low Infectivity challenge|
|High Infectivity Challenge||100||100||100||100||100|
Report Date: December 1990