Insulin-like growth factor binding proteins in the rat uterus and their regulation by oestradiol and growth hormone.
The rat uterus has previously been shown to be a site of insulin-like growth factor I (IGF-I) production and reception. The purpose of this study was to explore the possibility that the rat uterus can also hormonally regulate elaboration of IGF-binding proteins (IGFBPs). Uteri from adult ovariectomized rats were perfused, rinsed thoroughly and extracted. Western ligand blotting of SDS-polyacrylamide-fractionated uterine extracts revealed several bands of IGFBPs with molecular masses of 24, 28, 30-32 and 38-42 kDa; the 28 kDa protein was not detected in the serum. Hypophysectomy caused a marked decrease in 38-42 and 30-32 kDa proteins which was reversed by systematic treatment with growth hormone (2 x 120 micrograms per rat per day for 3 days). The 28 and 24 kDa proteins, however, were not altered by growth hormone. Oestradiol (1 microgram per rat per day for 3 days) induced more than a 50% decrease in both 38-42 and 28 kDa proteins, irrespective of the growth hormone status in ovariectomized rats. These studies disclose the multiplicity of uterine IGFBPs and show the ability of growth hormone and, more importantly, oestradiol to regulate these proteins. The ability of oestradiol to attenuate the IGFBPs in the uterus may enhance the access of endogenously produced IGFs to its cognate cell receptors and hence its cellular hormone action.
Yallampalli
C
C
Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston 77550.
Rajaraman
S
S
Nagamani
M
M
D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000032:analysis / Q000502:physiology*; D004958:Estradiol / Q000502:physiology*; D005260:Female; D013006:Growth Hormone / Q000502:physiology*; D007016:Hypophysectomy; D018969:Insulin-Like Growth Factor Binding Proteins; D010052:Ovariectomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013002:Somatomedins / Q000502:physiology*; D014599:Uterus / Q000737:chemistry / Q000502:physiology*
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D013002:Somatomedins; D004958:Estradiol; D013006:Growth Hormone