ORGAN-SPECIFIC EXPRESSION PATTERN OF THE HUMAN GROWTH-HORMONE PLACENTAL-LACTOGEN GENE-CLUSTER IN THE TESTIS

In addition to testosterone, the essential paracrine factor for sperma togenesis, a number of potential auto/paracrine regulatory substances such as beta-endorphins, enkephalins, chorionic gonadotropin beta, gro wth hormone-releasing hormone (GHRH) and insulin-like growth factor I (IGF-I) have been identified in the testis of various mammalian specie s. The latter findings prompted us to investigate a possible eutopic p roduction of GH, placental lactogen (PL) and PRL in human testes. Spec ific expression of testicular GH/PL mRNA (n = 20) was shown by reverse transcription-polymerase chain reaction (RT-PCR) using a pair of prim ers designed to non-selectively amplify any transcript of the five GH/ PL genes (GH-N, GH-V, PL-A, PL-B, PL-L). In contrast to the classical sites of production, the pituitary (exclusively GH-N transcripts) and the placenta (PL-A/B > 99%, GH-V < 1%), radioactive semiquantitative r estriction enzyme analysis of the PCR-products revealed, that the test is has its own organ-specific pattern of GH/PL gene expression: PL-A/B > GH-Y greater than or equal to PL-L = GH-N. All three organs express the single PRL gene, and testis and placenta show the alternative spl ice variant GH-V2. Immunological analyses by immunofluorometric assays for hPL-A/B, hGH-N and hPRL, demonstrated significant amounts of prot ein hormones in all testicular cytosolic homogenates (means: hPL 1.0 n g/g, hGH 5.1 ng/g and hPRL 58.7 ng/g tissue wet weight). Most notewort hy, hPL serum levels in an elderly age-matched healthy subjects (n=18) were <0.02 ng/ml. The concept of purely endocrine functions of placen tal and pituitary-derived GH/PL needs to be reassessed, since human te sticular synthesis of these molecules suggest auto/paracrine functions in the male reproductive tract. (C) 1997 Elsevier Science Ireland Ltd .