Comparison of the thermal stability characteristics of native and deglycosylated ovine pituitary lutropin.

The receptor binding, immunological and biological activities of native ovine lutropin were almost completely eliminated when aqueous solutions of the hormone were kept in a boiling water bath for 30 or 60 min. Similar exposure of chemically deglycosylated lutropin revealed that this preparation was relatively more stable to heat treatment. The conformational features of deglycosylated lutropin required for receptor binding and immunological activity were significantly retained after thermal treatment. The heated deglycosylated lutropin solution still retained its ability to antagonize cyclic AMP accumulation stimulated by the native hormone in rat testicular interstitial cells. Specificity of receptor (lutropin) binding or inhibitory activity was not lost by heating of deglycosylated lutropin as revealed by lack of an effect in follitropin radio-receptor assays.