Anatomy of the insulin-like growth factor system in the human testis.
OBJECTIVE
To study the cellular patterns of gene expression for insulin-like growth factors I and II (IGF-I and IGF-II), their receptors and specific high-affinity binding proteins (IGFBPs) in the human testis.


METHODS
In situ hybridization histochemistry was used to localize messenger ribonucleic acids (mRNAs) for IGF-I and IGF-II, the IGF-I and IGF-II receptors and IGFBP-1 to 6 in fresh-frozen testis sections from healthy young men who died of trauma.


RESULTS
Insulin-like growth factor I mRNA was not detected. Insulin-like growth factors II mRNA was abundant in testicular blood vessels and peritubular connective tissue. Both IGF-I and IGF-II receptor mRNAs were most abundant in the germinal epithelium. Insulin-like growth factor binding protein 1 mRNA was not detected. Binding protein-2 mRNA was expressed in both Leydig and Sertoli cells. Binding protein-3 mRNA was detected only in the endothelium of testicular blood vessels. Binding protein-4 mRNA was also localized in endothelium but, in addition, was present in Leydig cells and interstitial connective tissue. Binding protein-5 mRNA was abundant in connective tissue and was detected at low levels in Leydig cells. Binding protein-6 mRNA was present in some of the peritubular cells and in some cells of the interstitial compartment.


CONCLUSIONS
Our results suggest that IGFs may play significant roles in testicular function and germ cell development.
Zhou
J
J
Developmental Endocrinology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892.
Bondy
C
C
D000328:Adult; D001808:Blood Vessels / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis; D003238:Connective Tissue / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D017403:In Situ Hybridization; D018971:Insulin-Like Growth Factor Binding Protein 2; D018974:Insulin-Like Growth Factor Binding Protein 4; D018975:Insulin-Like Growth Factor Binding Protein 5; D018976:Insulin-Like Growth Factor Binding Protein 6; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D007335:Insulin-Like Growth Factor II / Q000096:biosynthesis*; D007985:Leydig Cells / Q000378:metabolism; D008297:Male; D012333:RNA, Messenger / Q000032:analysis* / Q000378:metabolism; D017526:Receptor, IGF Type 1 / Q000096:biosynthesis*; D017527:Receptor, IGF Type 2 / Q000096:biosynthesis*; D012708:Sertoli Cells / Q000378:metabolism; D013090:Spermatocytes / Q000378:metabolism; D013737:Testis / Q000033:anatomy & histology / Q000098:blood supply / Q000378:metabolism*
D002352:Carrier Proteins; D018971:Insulin-Like Growth Factor Binding Protein 2; D018974:Insulin-Like Growth Factor Binding Protein 4; D018975:Insulin-Like Growth Factor Binding Protein 5; D018976:Insulin-Like Growth Factor Binding Protein 6; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D017527:Receptor, IGF Type 2; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1