Thymidine and somatomedin-like activity of fetal pig sera: effect of fetal decapitation.
The effect of fetal decapitation on porcine serum thymidine and somatomedin activity was studied. Fetal decapitation, at 45 d of gestation, did not alter body weight when compared to controls at 110 d of gestation. Thymidine activity, measured as 3H-thymidine incorporation into rat L6 myoblasts in response to test sera, did not differ between decapitated (D) and control (C) fetal pig sera. Thymidine activity of fetal sera was low when compared to a postnatal normal pig serum pool (NPS) and approximately equal to that of a postnatal hypophysectomized pig serum pool (HPS). Somatomedin-like activity, measured as 35S-sulfate uptake into 110 d fetal costal cartilage, was similar in D and C sera and was low when compared to NPS. Postnatal cartilage, but not fetal cartilage, responded greater to NPS than to HPS when measuring somatomedin activity. This indicates that fetal cartilage may be sensitive to different factors than postnatal pig cartilage. Thymidine activity and somatomedin-like activity were also low in maternal sera when compared to NPS. The concentration of insulin-like growth factor-I (IGF-I) was lower in D sera when compared to C sera (0.26 +/- 0.03 vs 0.62 +/- 0.09 U/ml, respectively, p less than 0.05). It is postulated that locally produced growth factors, compared to circulating growth factors, may be more important determinants controlling the rapid growth rate of the fetus.
McCusker
R H
RH
Department of Foods and Nutrition, University of Georgia, Athens 30602.
Campion
D R
DR
D000818:Animals; D005314:Embryonic and Fetal Development / Q000502:physiology; D005260:Female; D005312:Fetal Blood / Q000378:metabolism*; D007016:Hypophysectomy; D010902:Pituitary Gland / Q000502:physiology; D011247:Pregnancy; D013002:Somatomedins / Q000378:metabolism*; D013552:Swine; D013936:Thymidine / Q000097:blood*
D013002:Somatomedins; D013936:Thymidine