Radioimmunoassay for porcine prolactin: plasma levels during lactation, suckling and weaning and after TRH administration.

A sensitive heterologous radioimmunoassay for porcine prolactin (pPRL) has been developed. Anti-ovine prolactin antibody was raised in rabbits which allowed a final dilution of 1:500 000. The separation of free and antibody bound [125I]pPRL is based on the double antibody solid phase system. The assay is specific for pPRL. There is no cross-reaction with pLH, pFSH and pTSH; little cross-reaction (1.35%) was found with pGH. The smallest detectable amount was 0.08 ng per tube. During lactation high plasma levels are found with great fluctuations. After weaning the plasma PRL levels fall to basal within a few hours. After thyrotrophin-releasing hormone (TRH) administration plasma concentrations increase within a few minutes.