Hormonal regulation of insulin-like growth factor gene expression in pig uterus.
The present studies were undertaken to define potential regulation of endometrial insulin-like growth factor-I (IGF-I) synthesis and secretion by steroid hormones and to correlate conceptus- and serum-derived estrogens with these events. Four experimental groups of gilts were studied: 1) prepubertal gilts administered estradiol (E) and/or progesterone (P4) daily for up to 15 days; 2) mature gilts ovariectomized (ovx) on day 2 of the estrous cycle, and then administered E, P4, or E plus P4 from days 4-11 after estrus; 3) unilaterally pregnant gilts on day 12 or 16 after the onset of estrus; and 4) cyclic gilts administered E on day 11 and hysterectomized 1, 6, 12, or 24 h after E. IGF-I mRNA was measured by blot hybridization of total cellular RNAs, while a specific RIA was used to quantitate levels of tissue and uterine luminal fluid (ULF) IGF-I. In prepubertal gilts, E or P4 increased uterine IGF-I mRNA levels and IGF-I protein. Mature, ovx gilts treated with E, P4, or E plus P4 had increased levels of endometrial IGF-I mRNAs and protein and luminal IGF-I. The magnitude of E or P4 induction was comparable and was not additive. Gravid horns on day 12 had higher amounts of IGF-I in ULF compared to day 12 nongravid horns or day 16 gravid and nongravid horns. However, no significant differences in the amounts of endometrial IGF-I mRNA and tissue IGF-I content between horns on each day were detected. Acute treatment of cyclic gilts (day 11) with E increased levels of endometrial IGF-I mRNAs and luminal IGF-I 1 h after treatment. The effect of E was transient and was reversed within 24 h of E injection. IGF-II and IGF-binding protein-2 mRNAs were regulated by E and P4 distinct from IGF-I mRNAs. These results indicate that E and P4 are involved in the normal regulation of uterine IGF-I synthesis and/or secretion. However, the relative contributions of serum and conceptus-derived estrogens in these processes during the preimplantation period in the pig remain to be defined.
Simmen
R C
RC
Department of Animal Science, University of Florida, Gainesville 32611-0701.
Simmen
F A
FA
Hofig
A
A
Farmer
S J
SJ
Bazer
F W
FW
D000375:Aging / Q000378:metabolism; D000818:Animals; D015152:Blotting, Northern; D004717:Endometrium / Q000378:metabolism; D004958:Estradiol / Q000502:physiology*; D004971:Estrus / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000378:metabolism; D010052:Ovariectomy; D011247:Pregnancy; D011374:Progesterone / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics; D017451:Receptors, Somatomedin; D013552:Swine; D014599:Uterus / Q000502:physiology*
D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D011374:Progesterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I