Effect of insulin-like growth factor I on deoxyribonucleic acid synthesis and galactopoiesis in bovine undifferentiated and lactating mammary tissue in vitro.
We have demonstrated that insulin-like growth factor I (IGF-I), at physiological concentrations, is a potent mitogen of bovine undifferentiated mammary epithelial cells cultured in collagen in serum-free medium. Its activity is independent of insulin, although at pharmacological concentrations insulin may substitute for IGF-I. The maximal [3H]thymidine incorporation stimulated by either IGF-I or insulin was only 25-40% of that in medium supplemented with 10% fetal calf serum (FCS) only. Epidermal growth factor (EGF) exhibited low mitogenic activity which was not synergistic with IGF-I in serum-free medium. IGF-I and EGF had low synergistic activity when added separately to 10% FCS-supplemented medium. Strong synergism (100% or more) was observed, however, when both factors were added simultaneously, indicating that their maximum mitogenic effect is dependent on a simultaneous presence of other factors existing in FCS. The galactopoietic effect of IGF-I was tested in organ culture of bovine lactating mammary gland. Neither fatty acid synthesis nor alpha-lactalbumin secretion was stimulated by IGF-I, even at 2000 ng/ml. These results indicate that, at least in our in vitro system, galactopoiesis is not affected by IGF-I.
Shamay
A
A
Department of Biochemistry and Human Nutrition, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot, Israel.
Cohen
N
N
Niwa
M
M
Gertler
A
A
D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis*; D004357:Drug Synergism; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005227:Fatty Acids / Q000096:biosynthesis; D005260:Female; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007768:Lactalbumin / Q000096:biosynthesis*; D007774:Lactation / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000378:metabolism*; D009924:Organ Culture Techniques; D011247:Pregnancy; D013002:Somatomedins / Q000494:pharmacology*
D005227:Fatty Acids; D007328:Insulin; D013002:Somatomedins; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D004247:DNA; D007768:Lactalbumin