Receptor binding and growth-promoting activity of insulin-like growth factor-I in a bovine mammary epithelial cell line (MAC-T3).
Insulin-like growth factor-I (IGF-I) has been known to be mitogenic to a variety of cell types, although a growth-regulatory role for IGF-I on bovine mammary epithelial cells has not been fully investigated. In the present study, we examined the receptor binding of IGF-I and its effect on growth in a bovine mammary epithelial cell line (MAC-T3). Specific receptors for IGF-I were detected on cultured bovine mammary epithelial cells. Competitive binding revealed that half-maximal inhibition of 125I-labelled IGF-I binding by IGF-I was approximately 3 micrograms/l. Dissociation rate constant of the IGF-I receptor was 3.10 +/- 0.06 nmol/l (S.E.M.) with a receptor site concentration of 366 +/- 8 fmol/mg protein for the average of three experiments. IGF-I exerted a positive mitogenic effect on MAC-T3 cells according to both direct DNA assay and thymidine incorporation assay. Moreover, the mitogenic effect of IGF-I on MAC-T3 cells was enhanced by the addition of fetal calf serum in the culture media. The present results suggest that the bovine mammary epithelial cell line (MAC-T3) provides a useful model system with which to study the biological actions of insulin-like growth factors on the bovine mammary secretory tissue in vitro.
Zhao
X
X
Department of Animal and Poultry Science, University of Guelph, Ontario, Canada.
McBride
B W
BW
Politis
I
I
Huynh
H T
HT
Akers
R M
RM
Burton
J H
JH
Turner
J D
JD
D000818:Animals; D002417:Cattle; D002460:Cell Line; D004848:Epithelium / Q000254:growth & development / Q000378:metabolism; D005260:Female; D007334:Insulin-Like Growth Factor I / Q000378:metabolism* / Q000494:pharmacology; D008321:Mammary Glands, Animal / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D008938:Mitosis / Q000187:drug effects*; D011485:Protein Binding
D007334:Insulin-Like Growth Factor I