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A Comparison of RIA and LC-MS/MS Methods to Quantify Steroids in Rat Serum and Urine Following Exposure to an Endocrine Disrupting Chemical
Citation:
Riffle, B., Matt Henderson, AND S. Laws. A Comparison of RIA and LC-MS/MS Methods to Quantify Steroids in Rat Serum and Urine Following Exposure to an Endocrine Disrupting Chemical. Presented at Society of Toxicology Meeting, March 10 - 14, 2013.
Impact/Purpose:
This abstract will be presented at the Society of Toxicology meeting, March 10-14, 2013, San Antonio, TX
Description:
Commercially available radio immunoassays (RIM) are frequently used in toxicological studies to evaluate effects of endocrine disrupting chemicals (EDCs) on steroidogenesis in rats. Currently there are limited data comparing steroid concentrations in rats as measured by RIM to those obtained using liquid chromatography coupled with tandem mass spectrometry (L-MS/MS). This study evaluates the concordance of serum and urine steroid concentrations as quantified by both RIA and LC-MS/MS following exposure to a known BOC, atrazine (ATR). Adult male rats were dosed with ATR. (200 mg/kg/d) or methylcellulose (solvent control) by oral gavage for 5 days. Animals were decapitated 2 hours after the final dose. Serum was collected and seperated into 2 aliquots for analysis. Serum were assayed by RIA for androstenedione (A), corticosterone (CORT), estradiol (E2), estrone (El). progesterone (P4), and testosterone (T). Serum was extracted via solid phase extraction prior to LC-MS/MS analysis with positive electrospray ionization in multiple-reaction monitoring mode for A, CORT, P4, and T. El and E2 serum concentrations were quantified similarly by LC-MS/MS, following derivatization with dansyl chloride. To compare CORT values from urine, pregnant adult rats were dosed with either ATR (100 mg/kg/d) or methylcellulose by oral gavage for 5 days (i.e., gestational days 14-18). Urine samples were collected daily for 2 consecutive 6 hour intervals following dosing and assayed for CORT by RIA and LC-MS/MS as described above. Data analyses demonstrated a high degree of correlation between the two detection methods (R2 = 0.88—0.92). No statistically significant differences were observed between RIA and LC-MS/MS means for any of the steroids assayed. These findings indicate that steroids may be reliably measured in rat biological media using RIAs or LC-MS/MS in toxicological studies. This abstract does not reflect US. EPA policy.