The theme of this Program Project proposal is that male reproductive tract tissue- and cell-specific sensitivity to hormonal stimuli is altered during aging. In this section, we seek to understand whether age-related changes in sensitivity to androgen occur, and if so, whether the mechanisms for change are intrinsic to the cells of androgen target tissues or if extrinsic factors are involved. The specific aims are: First, we will examine the mechanism controlling androgen sensitivity of the prostate and seminal vesicle by relating serum and tissue concentrations of testosterone (T), or its active metabolites dihydrotestosterone (DHT) and estradiol (E2) with biological markers for tissue structure, such as cell number, type and morphology, and with biological markers for tissue structure, such as cell number, type and morphology, and function, such as cell specific androgen responsive gene expression. From these initial experiments, we will learn the specific cell markers that are changing with age and whether or not these changes are related to the extracellular and/or intracellular steroid milieu. Second, we will determine whether age- associated intrinsic mechanisms within target cells affect androgen sensitivity. We will pharmacologically alter androgen receptor binding, 5alpha-reductase activity and DHT levels or aromatase activity and E2 levels in young and old rats and determine cell specific responsiveness of structure and function to T when intracellular steroid mechanisms are pharmacologically modified. Third, we will determine whether extrinsic factors from the testes of young or old rats affect androgen of sensitivity of target cell structure and function to T by inhibiting secretion of LH-stimulatable Leydig cell products, by eliminating Leydig cells with the cytotoxic agents, ethane dimethylsulfonate, and by orchiectomy. Growth within the individual prostatic lobes (ventral, lateral and dorsal) and seminal vesicle will be assessed by tissue weight and protein and DNA content; cell structure by microscopic examination of cell morphology and stereologic analysis of cell number within epithelial and stromal compartments; and function by Northern blots of specific mRNAs and Western blots of specific proteins for androgen receptor and 5a- reductase in all tissues, for prostatein, dorsal protein I and probasin the ventral, dorsal and lateral prostate lobes, respectively, and secretory protein IV in seminal vesicle and growth factors and their receptors in each tissue. Immunocytochemistry and in situ RNA hybridization will be used to identify specific cell types and to localize cell-specific expression of gene products under various hormonal and age-related conditions.