Syrian hamster proopiomelanocortin cDNA cloning and early seasonal changes in testicular expression.

Beta-endorphin (beta-End) and its precursor, proopiomelanocortin (POMC), are expressed in testis and beta-End stimulates testosterone secretion locally. We measured POMC expression in Syrian hamster testis following transfer from long days (LDs) to short days (SDs). We used RT-PCR to amplify partial-length hamster POMC cDNA to generate a probe for Northern analysis. We also used rat beta-End antiserum for radioimmunoassay analysis. SD exposure for 2 weeks decreased POMC mRNA and beta-End, but not testis weight or testosterone. We conclude that POMC signaling may play a role in seasonal regulation of testicular function.