We have recently demonstrated that the ventral prostate of adult rats contains high levels of pneumadin (PNM), a decapeptide originally isolated from mammalian lung, and that testosterone is needed for the maintenance of a normal level of the peptide in the prostate. Hence, we have investigated, by radioimmunoassay (RIA) and light ultrastructural immunocytochemistry (ICC), PNM concentration and localization in the rat ventral prostate during postnatal development. RIA showed that PNM content increased steadily from day 20 to day 90 of postnatal life, parallel to the increase in the prostate weight. In contrast, PNM concentration remained rather stable, although it showed a marked rise at day 40 when rat testes are known to reach their full maturation. ICC demonstrated that PNM immunoreactivity was mainly located in the apical pole of epithelial cells of rat ventral prostate, especially in the subcellular organelles involved in protein secretion, i.e. rough endoplasmic reticulum cisternae, vacuoles and granules. Taken together our study suggests the involvement of PNM in the functional control of rat prostate during postnatal maturation, although its exact role remains to be elucidated.

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