Cortisol in Poecilia latipinna: its identification and the validation of methods for its determination in plasma.

In vitro studies in which head kidney of Poecilia latipinna was incubated with labelled precursors have shown that cortisol is the only corticosteroid that could be detected as being produced by this tissue. Cortisol levels have been measured in the plasma of Poecilia latipinna by three methods. The routine use of two rapid and comparatively simple methods, the competitive protein binding assay and the radioimmunoassay, have been validated in terms of the more rigorous double isotope dilution derivative assay.