Rat ovarian insulin-like growth factor II gene expression is theca-interstitial cell-exclusive: hormonal regulation and receptor distribution.
While the potential role of insulin-like growth factor (IGF)-I in ovarian physiology has been extensively studied, relatively limited attention has been paid to IGF-II the very presence of which in the mature rat ovary has been questioned. In the present study, we have reevaluated rat ovarian IGF-II gene expression, its cellular localization, hormonal regulation, and site(s) of receptor interaction. IGF-II mRNA was detected in whole ovaries from immature as well as mature intact rats. Cellular localization studies revealed IGF-II transcripts in theca-interstitial but not granulosa cells (a site of IGF-I gene expression). In contrast, no cellular selectivity was noted for Type I and Type II IGF receptor gene expression, both of which were clearly detectable in both granulosa and theca-interstitial cells. In vivo treatment of immature hypophysectomized rats with diethylstilbestrol reduced ovarian IGF-II mRNA levels while increasing IGF-I mRNA levels. Taken together, these and previous observations reveal fundamental differences in the cellular localization and hormonal regulation of ovarian IGF gene expression in that IGF-II gene expression (unlike IGF-I) is theca-interstitial (rather than granulosa) cell-specific, and is subject to down (as opposed to up) regulation in response to estrogenic stimulation. In contrast, Type I and Type II IGF receptors exist on both somatic cell types of the rat ovary. These observations are consistent with the view that IGF-II of theca-interstitial cell origin may not only play an autocrine role but may also serve as one of several signals through which this androgen-producing cell may communicate in a paracrine fashion with the adjacent granulosa cell compartment.
Hernandez
E R
ER
Department of Obstetrics/Gynecology, University of Maryland School of Medicine, Baltimore 21201.
Roberts
C T
CT
Hurwitz
A
A
LeRoith
D
D
Adashi
E Y
EY
D000818:Animals; D004054:Diethylstilbestrol / Q000494:pharmacology*; D005260:Female; D015870:Gene Expression; D007016:Hypophysectomy; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D010053:Ovary / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000235:genetics* / Q000378:metabolism; D017451:Receptors, Somatomedin; D013799:Theca Cells / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects
D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D004054:Diethylstilbestrol