Use of an octadecylsilica purification method minimizes proteolysis during isolation of porcine and rat relaxins.

Previous attempts to purify relaxin from pregnant sow and rat ovaries have led to the identification of multiple components with very similar molecular weights (around 6000 daltons) and similar, but not identical amino acid compositions. It has been unclear whether these multiple forms of relaxin represented different allelic forms (isohormones), intermediates in a prohormone-hormone conversion, different hormones in their own right responsible for effects on different target tissues, or degradation products. We have applied a purification system using adsorption to small octadecylsilica (ODS) columns to reduce drastically the degree of heterogeneity. Both pig and rat relaxins are isolated as single major components with defined amino acid sequences and with minimal contamination by other molecular forms. These findings indicate that the relaxin heterogeneity previously observed is due to proteolysis of a single major stored form during conventional isolation procedures.