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Increasing information indicates that testosterone actions on cells are mediated not only through the classical intracellular androgen receptor (iAR), but also through membrane androgen receptors (mAR) on cell surfaces. Here, we investigate the expression pattern of mAR and iAR in thymic T cells, which is compared with that of splenic T cells. Thymic T cells are testosterone-sensitive in vivo, i.e. treatment of female C57BL/10 mice with testosterone for 3 weeks decreased the total number of thymic T cells by approximately 90%. The percentage of CD4(-) CD8(-) T cells increased, whereas that of the subsequent CD4(+) CD8(+) T cells was diminished. Flow cytometry and confocal laser scanning microscopy (CLSM) with different anti-iAR antibodies localized iAR predominantly in the cytoplasm, but not on the surface of thymic T cells. The iAR are functionally active since the iAR are induced by testosterone to translocate from cytoplasm to nucleus, and they bind the testosterone analogue 3H-R1881 with high affinity (K(d) approximately 2.2 nM) and saturable capacity (approximately 10,000 binding sites per cell) as determined by Scatchard analysis. By contrast, the impeded ligand testosterone-BSA-FITC (T-BSA-FITC) did not bind to the surface of thymic T cells. In accordance, testosterone was unable to induce any rapid rise in the intracellular free Ca(2+) concentration of Fura-2 loaded thymocytes. This indicates that thymic T cells do not express any significant amounts of mAR. Conversely, splenic T cells express functionally active mAR, whereas their expressed iAR are not functional in the genomic pathway. Our results support the view of a delicately balanced developmental regulation of iAR and mAR in T cells., (Copyright 2002 Elsevier Science Inc.)

We report the identification of a novel mouse cDNA encoding IAP38, a putative plasma membrane protein of 38 kDa in splenic macrophages, B cells and T cells. The expression of iap38 is induced by blood-stage infections of Plasmodium chabaudi malaria and is testosterone-sensitive in non-immune mice. However, when mice have acquired testosterone-resistant immunity to P. chabaudi, there is an about 40-fold increase in the expression of iap38, which has then largely lost its responsiveness to infection and testosterone. The gene iap38 is suggested to be involved in imparting spleen cells the ability to mediate testosterone-resistant immunity to P. chabaudi malaria.

The ubiquitous earthworm Enchytraeus buchholzi is provided with a very effective, but still unknown, mechanism of Cadmium (Cd)-detoxification, a central role in which has been ascribed to the Cd-inducible crp-gene encoding a novel cysteine-rich, non-metallothionein 25 kDa protein. This study identifies another Cd-responsive gene by differential screening of a cDNA-library constructed from Cd-exposed E. buchholzi. The isolated cDNA-clone designated Ebaldh encodes a putative aldehyde dehydrogenase. Northern blot analysis shows that the Ebaldh-expression is strongly enhanced by Cd, but remains unaffected by other stressors such as Zn, Hg, and H2O2. This Cd-specificity of Ebaldh suggests that Cd-detoxification in E. buchholzi requires low intracellular concentrations of aldehydes which are known to target sulfhydryl groups thus inactivating the Cd-binding capacity of CRP.

The expression of a novel Cd-inducible gene encoding a 25 kDa non-metallothionein cysteine-rich protein (CRP) in the earthworm Enchytraeus buchholzi is investigated with respect to Cd-specificity and Cd-sensitivity. The amount of CRP-mRNA correlates with the environmental as well as with the intra-worm Cd-concentration. Even the subtoxic concentration of 100 microgram Cd/1 induces CRP-gene expression. CRP-mRNA is expressed already 2 h after the worms were exposed to Cd. Other heavy metals or stress conditions can induce only little or even no CRP-mRNA. The CRP-gene is switched on long before Cd becomes toxic to worms and can be therefore taken as a warning signal of prospective irreversible Cd-damages at an early, still reversible stage.

Enchytraeus buchholzi (Oligochaeta) were exposed to various concentrations of CdCl2 in agar and aqueous solution. The Cd uptake was determined by atomic absorption spectroscopy as well as Cd effects on survival, reproduction, and mRNA synthesis by in vitro translation of total RNA in a rabbit reticulocyte lysate system. Although Cd was rapidly accumulated by the worms, any acute toxic Cd effects at concentrations below 4 mg Cd/liter were not detectable. However, such subtoxic Cd concentrations caused the induction of an mRNA species coding for a nonmetallothionein 33-kDa protein as revealed by 2D electrophoresis of in vitro translated in vitro translated proteins using [35S]methionine. The Cd-induced synthesis of this transcriptionally regulated protein might be a preindicator for a Cd intoxication in enchytraeids.