Detection and characterisation of transforming growth factor-beta in porcine colostrum.
Porcine colostrum and milk collected at different stages of lactation were assessed for transforming growth factor-beta (TGF-beta) activity using an epithelial cell bio-assay. A high level of TGF-beta activity was recorded in all colostrum samples after transient acidification treatment, ranging between 126 and 260 ng/ml for samples collected at the time of parturition and 73 ng/ml for the sample collected 12 h after parturition. Without transient acidification treatment TGF-beta activity was detected only in 2 samples collected at the time of parturition (12 ng/ml) and 12 h after parturition (9 ng/ml), respectively. TGF-beta activity was undetectable in milk collected 5 days after parturition. These results suggest that TGF-beta exists mainly in latent form in porcine colostrum and the concentration declines rapidly as lactation proceeds. After enrichment with cation exchange chromatography a low level of TGF-beta activity was detected in porcine milk. Further separation by size exclusion chromatography revealed two molecular mass forms of TGF-beta in both colostrum and milk samples, a major peak of about 80 kD and a minor peak of about 25 kD representing latent and active forms of TGF-beta, respectively. A further experiment showed that the latent form of TGF-beta in colostrum can be activated at pH 3.5 or less. It is speculated that TGF-beta found in the colostrum may play a physiological role in regulating postnatal adaptation of the gastro-intestinal tract in newborns.
Xu
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Department of Zoology, University of Hong Kong, China. xuruojun@hkucc.hku.hk
Doan
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Regester
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D000818:Animals; D002852:Chromatography, Ion Exchange; D003126:Colostrum / Q000737:chemistry*; D005260:Female; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007743:Labor, Obstetric / Q000378:metabolism; D007774:Lactation; D008892:Milk / Q000737:chemistry; D008970:Molecular Weight; D011247:Pregnancy; D012016:Reference Values; D013552:Swine; D016212:Transforming Growth Factor beta / Q000032:analysis* / Q000737:chemistry
D016212:Transforming Growth Factor beta