A new improvement of the sensitivity and specificity of radioimmunoassay for thyroliberin. Application to biological samples.

A new approach to increase the sensitivity and the specificity of a radioimmunoassay for thyroliberin (TRH) is described. The obtention of the anti-TRH antiserum used in this study has been previously reported (8): it exhibits a higher affinity for mono and di-iodo TRH derivatives. The method consists in iodinating the standards and the biological extracts with a large excess of reagents (NaI + chloramine T) under definite conditions of pH and concentrations. Mono iodo [[I125]-His2]-TRH purified by TLC was used as a tracer. This method both increases the sensitivity by 5 folds and improves the specificity by excluding or highly reducing the cross-reactivity obtained with closely related peptides. It has been successfully applied to mouse hypothalamic tissue extracts. It presents the advantage to measure low amounts of TRH in mouse tissue samples such as posterior pituitary and anterior pituitary.