Activin plays an essential role in the neuroprotection as a nerve survival factor.Activin receptor-interacting protein1(ARIP1)has been recently discovered in mouse brain as a regulator of activin signal transduction,however,its distribution pattern is not well characterized.In this study,the expression of ARIP1 mRNA and localization of mature ARIP1 protein in mouse tissues were examined by reverse transcription-polymerase chain reaction(RT-PCR)and immunohistochemistry,respectively.ARIP1 mRNA expression was detectable in cerebrum,cerebellum,extra-brain tissues such as pituitary,adrenal gland and testis.Immunohistochemical analysis showed that ARIP1-like immunoreactivity protein was mainly localized in hypothalamus and hippocampus of the cerebrum,Purkinje cells of the cerebellum,neurohypophysis and basophilic cells of adenohypophysis of the pituitary,adrenal cortex of the suprarenal gland,and Leydig cells of the testis.These data suggest that ARIP1 may participate in not only the regulation of activin signal transduction of nerve cells,but also the regulation of function in neural endocrine gland.