The use of blood mRNA technology to detect abuse with GH and IGF-I in sport
The detection of exogenously administered rhGH and rhIGF−I poses a formidable challenge as these proteins are identical to the endogenously produced hormones. Messenger Ribonucleic Acid (mRNA) transcripts for GH and IGF-I are translated into these proteins intracellularly. Tissue specific mRNA is present in small but quantifiable levels in the circulation.
It is known that mRNA encoding GH and IGF−I are present in the circulation. Injection of exogenous rhGH, rhIGF−I or rhIGF−I/rhIGFBP−3 would be expected to modify circulating levels of endogenous hormones, by action on the negative feedback control mechanisms associated with the GH−axis. Synthesis of mRNA encoding these hormones may also be affected.
Measurement of circulating mRNA encoding these peptides would circumvent some of the limitations associated with the conventional immunoassay methods for measuring proteins. Reverse Transcription PCR (RT−PCR) of the mRNAs of the specific markers mentioned above, followed by real time quantitative PCR (qPCR) of the transcribed cDNAs could allow early, specific and sensitive detection of exogenous hormone injection. We have shown in preliminary studies that mRNA for GH can be detected in the peripheral circulation and this raises the possibility of using these markers in the detection of exogenous administration of GH and IGF-I.
There are several potential advantages of this technique. Firstly, multiple markers can be measured in a single assay using different primers which would reduce the cost and time needed to undertake the test. Secondly, once the blood has been collected, the mRNA is stable at room temperature which means the sample can be transported as whole blood at room temperature.
We are undertaking a pilot project to assess the intra-individual variability of mRNA concentrations specific to proteins in the GH-axis. mRNA concentrations will be monitored over 6 weeks in 10 healthy volunteers who are fit and exercise regularly. We will then assess the acute changes in circulating mRNA in response to four injections of rhGH in 10 healthy volunteers.