Radioimmunoassay (RIA) of Serum Corticosterone in Rat

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Abstract
A radioimmunoassay for corticosterone was developed and characterized using corticosterone antiserum and a simple ethanol extraction procedure. The antiserum-appeared to be highly specific for corticosterone. Intrassay variability was 3.67 .+-. 0.75% (mean .+-. SE) at 50 pg of corticosterone; interassay variability with a mean value of 51.15 pg was 6.98 .+-. 1.01%. Assay sensitivity was 9.48 .+-. 0.60 pg. Using this assay, serum obtained from adrenalectomized and adrenalectomized-ovariectomized rats yielded lower corticosterone values than serum from intact or ovariectomized rats. Intact females had lower corticosterone values than intact males. Rats exposed to elevated temperature (32.5.degree. C) displayed significantly (P < 0.001) elevated plasma corticosterone levels (48.48 .+-. 4.37 .mu.g/100 ml) compared to control (24.5 .degree. C) animals (21.31 .+-. 2.02 .mu.g/100 ml). The high specificity, sensitivity, precision, recovery level and ease of this technique make it useful for the study of either serum or plasma corticosterone.