EXPRESSION AND REGULATION OF NEUROPEPTIDE-Y MESSENGER-RIBONUCLEIC-ACID IN CULTURED IMMATURE RAT LEYDIG AND SERTOLI CELLS

Neuropeptide Y (NPY) potentiates the release of gonadotropins fi om th e pituitary in response to GnRH in the hypothalamus and modulates repr oductive function. In the present study, we showed that 1) specific or gans in the male rat reproductive tract express NPY messenger RNA (mRN A); 2) the multifactorial regulation of NPY mRNA in rat Leydig and Ser toli cells is temporally and hormonally regulated in vitro; 3) both Se rtoli cell factor(s) and germ cell factor(s) potentiated to stimulate NPY gene levels in Leydig cells; and 4) intense NPY immunoreactivity w as detected in cultured Leydig cells. Using the RT-PCR method, we foun d that Leydig cells, Sertoli cells, epididymis, and vas deferens expre ssed NPY mRNA, whereas germ cells, seminal vesicle, and prostate did n ot. Northern blot analyses showed that NPY mRNA was not expressed in f reshly isolated immature Leydig cells, but that NPY mRNA levels were i ncreased by the addition of LH, cytokines such as interleukin-1 alpha and -1 beta, forskolin, or phorbol 13-myristate 12-acetate. NPY mRNA l evels in immature Sertoli cells were also increased by FSH. In additio n, a germ cell factor(s) secreted from pachytene spermatocytes or roun d spermatids purified by centrifugal elutriation as well as a Sertoli cell factor(s) stimulated by FSH increased NPY gene levels in Leydig c ells. Immunocytochemical analyses showed that the immunostaining was m ore marked in Leydig cells than in Sertoli cells in vitro. These findi ngs indicate that testicular NPY gene expression is induced in Leydig cells or Sertoli cells by gonadotropins or cytokines within the testes , and that factors secreted from Sertoli cells or germ cells affect NP Y gene expression in Leydig cells in vitro. Our findings suggest that NPY expressed in the reproductive system may modulate reproductive fun ction as well as that in the nervous system.