298 M H ABEL and others . Effects of FSH on testicular transcript levels Figure 3 Real-time PCR measurements of Sertoli cell-speciﬁc mRNA transcript levels in testes from adult hpg mice treated for 0 (control), 12, 24 or 72 h with FSH. Results show the meanGS.E.M. of three or four animals per group. Groups with different letter superscripts are signiﬁcantly different; where no superscripts are shown there was no difference between groups. is an excellent model system with which to test the effects of FSH since the Sertoli cells have not been exposed to the hormone but express FSHR and are sensitive to FSH action. This study is an extension of earlier work by Sadate-Ngatchou et al. (2004) using a longer treatment period, different array chips with a larger characterised gene set (MOE430A chips (14 000 characterised genes) versus MG U74Av2 chips (6000 characterised genes, 6500 ESTs)), a signiﬁcantly larger animal cohort and recombinant FSH. In addition, the purpose of this study was to follow changes in testicular transcript levels in the hpg in response to maintained levels of FSH rather than the acute response to a single administration. Together, the two studies complement Journal of Molecular Endocrinology (2009) 42, 291–303 each other and serve to identify transcripts regulated by FSH over the short and medium term. Interestingly, at 12 h after the start of FSH administration, when both studies can be directly compared with a degree of caution, there were only 44 differentially transcripts common to both studies, 25 up-regulated (e.g. Cyp17, Ren1, Fos, Hdc, Col4a1) and 19 down-regulated (e.g. Rgs11, Cdo1, Erbb3, Ptk2b, Vnn1). This low number of transcripts in common may be due to a combination of the chips used, the age of the animals, the number of animals used and the treatment regime. In this study, the total number of transcripts altered at each time point did not vary markedly across the treatment period but only 39 transcripts were www.endocrinology-journals.org