Newly Synthesized Proteins in Seminiferous Intertubular and Intratubular Compartments of the Rat Testis1

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Abstract
Two-dimensional gel electrophoresis combined with autoradiography and Western blot procedures has been used to characterize newly synthesized proteins in testicular intertubular fluid (TIF) and seminiferous tubular fluid (SNF). Fluids were collected following in vivo and in vitro intratesticular injection of [35S]methionine into control and hypophysectomized adult rats. A discrete number of [35S]methionine-labeled proteins were detected within TIF and SNF. Their presence and relative abundance varied according to in vivo and in vitro labeling conditions. While two major blood plasma proteins, albumin and transferrin, were radioactively labeled after in vivo labeling, these two proteins were insignificantly labeled in samples collected after in vitro labeling. Three acidic proteins, possibly secreted by Sertoli cells (Mr=72,000, 45,000 and 35,000), were more abundant in TIF samples collected after in vitro [35S]methionine labeling than after in vivo labeling. Incubated seminiferous tubules and TIF of hypophysectomized rats showed a decrease in [35S]methionine-labeling intensity of the Mr=72,000 acidic protein, possibly reflecting changes in the seminiferous epithelium caused by pituitary hormonal deprivation. Autoradiographs of TIF and most remarkably, of SNF, showed many protein spots that suggested cell breakage and leakage during sample collection. Results of this study suggest that most albumin and transferrin found in TIF and SNF have an extratesticular origin and that proteins secreted by the Sertoli cell can give access to both TIF and SNF.