Further characterization of a steroid receptor-active protease from the mature rabbit epididymis

Maternal Protein Restriction Alters the Expression of Proteins Related to the Structure and Functioning of the Rat Offspring Epididymis in an Age-Dependent Manner

Nutrition is an environmental factor able to activate physiological interactions between fetus and mother. Maternal protein restriction is able to alter sperm parameters associated with epididymal functions. Since correct development and functioning of the epididymides are fundamental for mammalian reproductive success, this study investigated the effects of maternal protein restriction on epididymal morphology and morphometry in rat offspring as well as on the expression of Src, Cldn-1, AR, ER, aromatase p450, and 5α-reductase in different stages of postnatal epididymal development. For this purpose, pregnant females were allocated to normal-protein (NP—17% protein) and low-protein (LP—6% protein) groups that received specific diets during gestation and lactation. After weaning, male offspring was provided only normal-protein diet until the ages of 21, 44, and 120 days, when they were euthanized and their epididymides collected. Maternal protein restriction decreased genital organs weight as well as crown-rump length and anogenital distance at all ages. Although the low-protein diet did not change the integrity of the epididymal epithelium, we observed decreases in tubular diameter, epithelial height and luminal diameter of the epididymal duct in 21-day-old LP animals. The maternal low-protein diet changed AR, ERα, ERβ, Src 416, and Src 527 expression in offspring epididymides in an age-dependent manner. Finally, maternal protein restriction increased Cldn-1 expression throughout the epididymides at all analyzed ages. Although some of these changes did not remain until adulthood, the insufficient supply of proteins in early life altered the structure and functioning of the epididymis in important periods of postnatal development.

A nuclear binding assay for measurement of biologically active androgen receptors in animal tissues and human prostate cancer

A nuclear binding (NB) assay has been developed for the measurement in intact viable cells of biologically active (functional) estrogen and progesterone receptors, i.e. those capable of binding to nuclear acceptor sites [Spelsberg et al., Endocrinology 121: 631 (1987)]. This paper describes the application of this assay to analyses of androgen receptors in the guinea pig seminal vesicle and in human prostatic carcinoma. Cells from fresh animal seminal vesicles or human prostate carcinoma are isolated using collagenase and are incubated with [3H]R1881 for 1 h at 22 degrees C, after which nuclei are isolated at 4 degrees C and assayed for DNA and radioactivity. This NB assay demonstrates a saturable, temperature dependent, steroid and tissue specific nuclear binding of [3H]R1881 for the guinea pig-seminal vesicle system. The nuclear binding is of high affinity and low capacity. The NB assay reveals several important aspects of the androgen and estrogen receptors in target tissues: (1) the nuclear acceptor sites for androgen receptor (AR) are steroid receptor specific; (2) there are different concentrations of the androgen and estrogen receptors between the epithelium and the fibromuscular components of the guinea pig seminal vesicle; and finally (3) some biopsies of human prostate cancer appear to contain biologically inactive AR. This assay may be useful in the analyses of functional receptors in biopsies of human cancer cells.

A protease acting on the estrogen receptor may modify its action in the adult rabbit epididymis

We have previously shown that the cytosolic estrogen receptor in adult rabbit epididymides sediments as an congruent to 3 S species on sucrose gradients containing 0.01 M KCl while that from immature rabbit epididymides sediments at congruent to 9 S. This age-dependent decrease in sedimentation coefficient is attributable to the appearance of a leupeptin-sensitive protease as the animals mature. We now show that if adult epididymides are homogenized in buffer containing leupeptin, the 9 S receptor can be demonstrated, indicating inhibition of receptor degradation. In vitro nuclear uptake studies conducted in the absence of leupeptin indicated that the proteolyzed receptor was not an efficient nuclear binder. When leupeptin was present, nuclear uptake increased 6-fold and it was accompanied by depletion of receptor from the cytosol. Binding of the receptor to nuclei was specific since it could be inhibited by unlabeled estrogens but not by unlabeled 5 alpha-dihydrotestosterone or progesterone. In vitro mixing experiments indicated that the proteolytic activity was associated with the crude nuclear fraction since, in the absence of leupeptin, they had reduced ability to bind estrogen receptor present in immature epididymal cytosol. Specific in vivo binding of [3H]estradiol by adult and immature rabbit epididymides could be demonstrated. The time course of in vivo binding of [3H]estradiol by adult rabbit epididymal nuclei indicated maximum binding (70 fmol/g tissue) at 30 min following injection. By 60 min, the amount of binding had decreased to about 25 fmol. The accessory sex organs, which do not contain the protease, also exhibited maximum binding (150 fmol/g tissue) at 30 min. However, at the 60 min period binding was still about 140 fmol. Processing the tissues in buffers containing leupeptin had no effect on the results obtained. These results are interpreted to indicate that the presence of the protease decreases nuclear binding of the estrogen receptor and shortens nuclear occupancy. This combination of factors may be responsible for the decrease in estrogen action in the adult rabbit epididymis.