Bioassays

SASCO CF-1 Mouse

Hormone immunoactivity does not always equal hormone bioactivity.
When the scientific questions asked require bioactive answers, then a bioassay is performed. In addition to answering a different question, the bioassay is also more sensitive than it's immunoassay counterpart and can detect hormones at levels which would be otherwise undetectable in an immunoassay.

Because the bioassay is more sensitive, assays can be done using very small sample volume reducing the need for larger sample collections.

Currently, we are running a Mouse Interstitial Cell Testosterone (MICT) bioassay which measures both luteinizing hormone (LH) and chorionic gonadotrophic hormone (CG) in a variety of species and materials, including rhesus serum, marmoset plasma, tamarin urine and cell culture media.

Bio & Immuno LH

Bio & Immuno LH

This graph shows both the bioactive and immunoactive profiles of LH in rhesus female serum pooled from days -7 to +3 of their ovulation cycle. As you can see, the bioactive LH starts out below the immunoreactive LH but is markedly higher on the day of ovulation.

The bioassay is often used to validate the corresponding immunoassay for that hormone. A correlation coefficient (r) near +1 will show a good positive relationship between the bioactive and immunoactive measurements.

Because the bioassay requires a testosterone RIA follow-up assay making the bioassay more expensive, often the immunoassay is preferred over the bioassay if the values for both assays are highly similar.

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