Stimulation of DNA synthesis in cultures of ovine mammary epithelial cells by insulin and insulin-like growth factors.
Ovine mammary epithelial cell clumps (30-90 microns) were plated onto attached gels of rat tail collagen in serum-free medium. Synthesis of DNA by these cultures could be stimulated by insulin-like growth factor-I (IGF-I) with a median effective dose of 5 micrograms/l, irrespective of stage of pregnancy. The time-course of response, however, was significantly slower in cells prepared from mammary tissue of non-pregnant and early pregnant sheep compared with sheep later in pregnancy. IGF-II had approximately 10% of the potency of IGF-I in stimulating DNA synthesis. Insulin acted over a wide concentration range and produced a maximum rate of stimulation not significantly different from that produced by IGF-I. These results are consistent with actions through the type-I IGF receptor although insulin may also act through its own receptor, possibly stimulating local IGF-I production. It is concluded that IGF-I is an important mitogen for ovine mammary epithelial cells.
Winder
S J
SJ
AFRC Institute for Grassland and Animal Production, Hurley, Maidenhead, Berkshire.
Turvey
A
A
Forsyth
I A
IA
D000818:Animals; D002455:Cell Division; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis*; D004848:Epithelium / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology; D008321:Mammary Glands, Animal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011247:Pregnancy; D012756:Sheep / Q000378:metabolism*; D013002:Somatomedins / Q000494:pharmacology*
D007328:Insulin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D004247:DNA