Immunolocalization and expression of insulin-like growth factor I (IGF-I) in the mammary gland during rat gestation and lactation.
We have studied the physiology and tissue expression of IGF-I and IGF-BP3 in pregnant and lactating rats. Specific assays (radioimmunoassays and a binding protein assay) were used to measure serum IGF-I, IGF-II, and IGF-BP levels. IGF-I and IGF-BP3 expression levels were determined in mammary gland and liver by slot-blotting. A sensitive and IGF-I-specific ribonuclease (RNAse) protection assay was further used to detect RNAs transcribed from the IGF-I gene. In the first half of pregnancy, the maternal serum IGF-I concentration rises while the IGF-BP level decreases. This may modify IGF-I availability, thus promoting rapid tissue growth and differentiation. In the second half of pregnancy, the mean serum IGF-I concentration falls sharply from 1140 +/- 150 ng/ml at seven days of pregnancy to 470 +/- 85 ng/ml at 20 days. Post-partum, serum IGF-I increases back to the level obtained in non-pregnant controls within 5 days. Serum levels of IGF-BP, during the same two periods, follow a similar pattern, decrease during pregnancy and increase after parturition. No IGF-II was detected at any time. From the onset of pregnancy to term, IGF-I gene expression in the mammary gland diminishes. In the liver, on the other hand, expression increases during very early pregnancy and diminishes thereafter, remaining below the level measured in non-pregnant animals from mid-pregnancy to term. The pattern of IGF-BP3 expression followed was similar in both organs, with a decrease during gestation.(ABSTRACT TRUNCATED AT 250 WORDS)
Marcotty
C
C
Service de Biochimie Humaine, Université de Liège, Belgium.
Frankenne
F
F
Meuris
S
S
Hennen
G
G
D000818:Animals; D002352:Carrier Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D007124:Immunoenzyme Techniques; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000032:analysis* / Q000235:genetics* / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D007774:Lactation / Q000502:physiology*; D008099:Liver / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000737:chemistry* / Q000378:metabolism*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012260:Ribonucleases
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D012260:Ribonucleases