Germ cell development within the mammalian testis requires testosterone stimulation of somatic Sertoli cells via interaction with intracellular androgen receptors (AR). AR expression levels undergo marked changes during spermatogenesis suggesting that the modulation of AR expression is an important mechanism to regulate Sertoli cell responsiveness to testosterone. An analysis of the AR gene promoter revealed three kappaB enhancer elements that interacted with Sertoli cell p50 and RelA NF-kappaB proteins, and the overexpression of these NF-kappaB subunits in Sertoli cells stimulated AR promoter activity. Moreover, TNF-alpha, a secretory product of round spermatids, stimulated NF-kappaB binding to the AR promoter, induced AR promoter activity, and increased endogenous AR expression in primary cultures of Sertoli cells. Given the requirement of testosterone for spermatogenesis and the importance of AR in mediating Sertoli cell responsiveness to testosterone, the stimulation of AR expression by NF-kappaB and TNF-alpha may represent an important regulatory mechanism required to maintain efficient spermatogenesis.