Isolation and characterization of fin whale prolactin

A highly purified prolactin preparation has been obtained from fin whale pituitaries by extraction with acid acetone. salt precipitation, isoelectric fractionation, and exclusion chromatography on Sephadex G-100 and ion-exchange chromatography on DEAE-CELLULOSE. Fin whale prolactin was isolated in a yield of 250 mg/kg wet weight tissue. It was found to have a molecular weight (SDS disc gel electrophoresis) of 23,600 daltons and an alpha-helix content (circular dichroism) of 50%. The amino acid composition and circular dichroism spectra were very similar to those of porcine prolactin. The partial amino acid sequence has been determined by the method of fluorescein-isothiocyanate. Fin whale prolactin was found to be 80% as potent as ovine prolactin with regard to pigeon crop-sac assay.