Insulin-like growth factor I (IGF-I) regulates endocrine activity of the embryonic testis in the mouse.
Insulin-like growth factor I (IGF-I) is important for gonadal and reproductive functions in mammals, although the physiological role of this growth factor during gonadal development in rodents remains largely unknown. Here, we examined the steady-state levels of IGF-I mRNA by the reverse transcriptase polymerase chain reaction (RT-PCR). IGF-I protein expression was also detected by Western blot. The effect of IGF-I as promoter of 17alpha-hydroxylase/C17-20 lyase and 17beta-hydroxysteroid dehydrogenase enzyme activity in vitro was evaluated by radioimmunoassay. Onset of IGF-I gene expression was on day E10 (urogenital ridge stage). IGF-I mRNA expression was markedly reduced on days E12 and E13 (testicular differentiation stage). IGF-I transcripts increased on day E14 and their transcription levels were maintained throughout the stages analyzed. Several IGF-I protein bands of 31-100 kDa were observed. Culture experiments demonstrated that 17alpha-hydroxyprogesterone and testosterone (T) secretion levels increased in the presence of IGF-I on days E11-E17. Additive effects of IGF-I plus (Bu)2cAMP were also seen during testicular development. It is proposed that IGF-I regulates the expression of key steroidogenic enzymes important for endocrine activity of the testis during prenatal development leading to establishment of the male phenotype and fertility.
Villalpando
Irma
I
Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apartado Postal 70228, CP 04510 Mexico City DF, Mexico. mirma@servidor.unam.mx
López-Olmos
Victoria
V
D015067:17-Hydroxysteroid Dehydrogenases / Q000378:metabolism; D000818:Animals; D004622:Embryo, Mammalian; D004703:Endocrine System / Q000196:embryology / Q000201:enzymology / Q000378:metabolism*; D005865:Gestational Age; D006066:Gonads; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000502:physiology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D012333:RNA, Messenger / Q000032:analysis; D013254:Steroid 17-alpha-Hydroxylase / Q000378:metabolism; D013737:Testis / Q000196:embryology* / Q000378:metabolism; D013739:Testosterone / Q000096:biosynthesis
D012333:RNA, Messenger; D013739:Testosterone; D007334:Insulin-Like Growth Factor I; D015067:17-Hydroxysteroid Dehydrogenases; C044256:3 (or 17)-beta-hydroxysteroid dehydrogenase; D013254:Steroid 17-alpha-Hydroxylase