Science - December 10, 2010

New screening test for prohormones

With the new screening method developed by Jeroen Rijk at RIKILT, the presence of banned prohormones in meat can now be exposed.

Prohormones are the precursors of hormones: substances that are converted by enzymes in the body into growth hormones. Bodybuilders use prohormones, and so occasionally do beef and veal farmers.

The prohormones can be added to feeds or given in the form of pills or injections. Rijk first tested whether the substances occasionally found in farm animals really are converted into hormones in the bodies of lab animals. Then he found three methods of identifying prohormones in the lab.

Rijk can reveal the presence of prohormones in livestock feed using a bioassay in which he uses a liver extract that contains the enzymes needed to convert the prohormones into hormones.
Rijk can also identify a prohormone in the animal's urine. To do this he made a 'urine profile' of cattle with and without prohormones. Hormones are naturally present in the urine of both groups, but by looking at the differences in the urine composition, Rijk can track down abuse of prohormones.
 Gene expression
A third method of tracing prohormones is by measuring the gene expression in the liver of cattle. The gene expression can be read from the amount of RNA.  If Rijk finds certain deviations in the RNA in liver samples, this can be a sign of prohormone use. Unlike the other two methods, this method is not yet ready for more general use.