Mol Reprod Dev 2001 Sep 01;601:56-64. doi: 10.1002/mrd.1061.

Mammalian follicle-stimulating hormone and insulin-like growth factor I (IGF-I) up-regulate IGF-I gene expression in organ culture of newt testis.

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We previously showed that porcine follicle-stimulating hormone (pFSH) and human recombinant insulin-like growth factor (rhIGF-I) promote the differentiation of secondary spermatogonia into primary spermatocytes in organ cultures of newt testes, respectively. To elucidate the molecular action of FSH and IGF-I, we cloned cDNAs for newt IGF-I and IGF-I receptor (IGF-IR), and examined their mRNA expression in organ culture during newt spermatogenesis. Northern blot and reverse transcription-polymerase chain reaction (RT-PCR) analyses revealed that IGF-I mRNA was highly expressed in somatic cells (mostly Sertoli cells) at the secondary spermatogonial stage but barely in germ cells, and that IGF-IR mRNA was expressed in both germ and somatic cells at all stages examined. The addition of pFSH to newt testis markedly increased IGF-I mRNA expression. Also, rhIGF-I increased IGF-I mRNA expression, whereas IGF-IR mRNA expression declined slightly. These results suggest that the ability of FSH to promote the differentiation of secondary spermatogonia is at least partly mediated by somatic cell-derived IGF-I, and that IGF-I mRNA expression in somatic cells is auto-upregulated.

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Species referenced: Xenopus
Genes referenced: igf1 ins