Ultimately the primary function of all somatic cells in the testis is to ensure a microenvironment that provides adequate androgen and nutritive support for spermatogenesis and confers immunologic tolerance for the mitotic spermatogonia located outside the blood-testis barrier. It is well known that the pituitary hormones LH and PRL affect androgen secretion by Leydig cells. What is less well understood is the identity and function of the local peptidergic factors that make up the non- steroidal microenvironment of the interstitium. LACAF is an interstitial cell protein stimulated by HCG and growth factor but inhibited by prolactin. LACAF activates adenylyl cyclase in Leydig cells but this activation is not functionally directed towards steroidogenesis. Such differential regulation is by known Leydig cell trophic factors suggests that LACAF is an autocrine regulatory factor. This protein shows some sequence homology with the testicular protein of the VIP family of peptides that shares this capacity to activate cyclase without concomitant effects on steroidogenesis. We will study the function and regulation of these two proteins in parallel. Prolactin preferentially enhances the secretion of two other interstitial proteins, one of which is a known immunomodulator, suggesting the prolactin affects testicular immune elements. The second protein, PIL, may be a member of the transforming growth factor Beta family of peptides. The physiological significance of this regulated pattern of interstitial proteins is presently unknown. Our proposed studies will focus on the unique features of the regulation of LACAF, PIL and complement components by prolactin. The ability to determine the various forms of the prolactin receptor MRNAS affords the opportunity to determine the cell-specificity of these prolactin-induced changes in interstitial protein secretion. LACAF and PIL proteins will be further characterized. Cloned CDNAS for these interstitial proteins will be isolated and their structure characterized. Moreover, specific probes will be generated for use in determining both physiological and aberrant expression of these proteins in vivo and in vitro studies. Regulation of these interstitial proteins will be studied by analysis of their MRNA levels as a function of endocrine status using hybridization in situ and immunohistochemistry. The mechanism(s) of action of these peptides will be investigated by assessment of their effects on both seminiferous tubule and interstitial cell function. This research plan will lead to new, significant data on the mediators of intratesticular signalling and their physiological relevance in the testis.
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