Transcripts of the PACAP gene have been detected by in situ and Northern hybridizations in adult testes , and by immunocytochemistry PACAP immunoreactiv-ity has been found in spermatogonia and primary spermatocytes, but not in mature spermatids or spermatozoa , or in Sertoli and Leydig cells . These findings suggest that PACAP may function as a paracrine or autocrine regulatory factor for germ cells with specific function during early spermatogenesis, and probably with other effects in the fetal period.
Many details about the role of VIP and PACAP-27 in fetal life still remain obscure. We do not know whether their site of synthesis is the mother, placenta, or fetal tissues. Nor do we know their target cells in the fetus, or their physiological concentrations in fetal serum and testes. Although an effect on fetal Leydig cells was demonstrated, its physiologic significance still remains unclear. buy levaquin online
In conclusion, this study has shown that fetal testicular steroidogenesis initially starts independently of pituitary gonadotropin stimulation and can be stimulated by nongon-adotropic endocrine or paracrine factors, although a constitutive component in the onset of steroidogenesis is also possible. The specific effects of VIP and PACAP-27 on fetal Leydig cells demonstrates that nongonadotropic factors can be powerful stimuli of their function. However, the identity of the most important regulatory factors in vivo remains to be elucidated.