PROOPIOMELANOCORTIN (POMC) GENE-EXPRESSION, AS IDENTIFIED BY IN-SITU HYBRIDIZATION, IN PURIFIED POPULATIONS OF INTERSTITIAL MACROPHAGES ANDLEYDIG-CELLS OF THE ADULT-RAT TESTIS

The presence of testicular pro-opiomelanocortin (POMC) mRNA and POMC-d erived peptides has recently been demonstrated in purified preparation s of interstitial macrophages and in Leydig cells of the adult rat tes tis by Northern blot analysis and immunocytochemistry. In the present study, in situ hybridization provided further evidence that the POMC g ene is expressed by both purified interstitial macrophages and Leydig cells. The cellular localization of the POMC transcripts was similar f or both cell types, silver grains being predominantly located in the c ytoplasm. The specificity of the labelling was demonstrated by the lac k of silver grains in the preparations pretreated with RNAase or hybri dized with an insulin cDNA probe, a gene known not to be expressed in these cell types. An additional control was provided by hybridization with a sense POMC RNA probe, which gave a less intense signal when com pared with the antisense RNA probe under the same experimental conditi ons. The results confirm POMC gene expression in both macrophages and Leydig cells in the adult rat testis.