[The dimer form of porcine prolactin]

The properties of a previously isolated disulfide form of pituitary porcine prolactin (pPRL) were studied. Using the immunoblotting technique and anti-pPRL antiserum it was shown that the disulfide dimeric form occurred at every stage of pPRL purification. The biological activity of this form was 11.76 +/- 0.59 IU/mg in comparison with the 2nd International standard of ovine PRL when tested in vivo in pigeon cropsac assay. Immunoelectrophoresis with antiserum to the disulfide dimer of pPRL did not reveal any qualitative differences between this form of the hormone, glycosylated and nonmodified variants of pPRL. The potential physiological role of the form of disulfide dimers in the pituitary gland and circulation was discussed.