Effects of an antiandrogen, cyproterone acetate, on the kidney of the three-spined stickleback (Gasterosteus aculeatus L.)

Vitellogenin synthesis via androgens in primary cultures of tilapia hepatocytes

Involvement of androgens in vitellogenin (VTG) synthesis was investigated using the primary hepatocyte cultures of tilapia, Oreochromis mossambicus. Concentration of VTG in the medium was assessed by enzyme-linked immunosorbent assay. When the hepatocytes of females were treated with testosterone (T), 17 alpha-methyltestosterone (MT) and 5 alpha-dihydrotestosterone (DHT), VTG concentration in the medium slightly increased or maintained. DHT, but not T and MT, increased VTG in the medium of male hepatocyte cultures. However, VTG production in the male hepatocytes, which were previously treated with estradiol-17 beta (E(2)), maintained high level by treatment of T. Similarly, co-treatment of E(2) and the androgens to the male hepatocytes enhanced VTG concentration in the medium. These results suggest that the androgens have some roles in VTG synthesis in the hepatocytes. Tamoxifen, a nonsteroidal antiestrogen, reduced VTG synthesis by the androgens. On the other hand, co-treatment of T and fadrozole, an aromatase inhibitor, failed to inhibit the effect of VTG synthesis by T alone. Analysis with RT-PCR did not demonstrate expression of the brain and the ovarian types of aromatase mRNA in the liver. These results suggest that the possibility of local aromatization of the androgens in the tilapia liver is low and that androgens bind estrogen receptor and, consequently, exert estrogenic action. Treatment of cyproterone acetate, an antiandrogen reagent, increased production of VTG with DHT. Involvement of androgens might not be ignored in regulation of VTG synthesis in the liver.

Specific binding of 11-ketotestosterone in an androgen target organ, the kidney of the male three-spined stickleback,Gasterosteus aculeatus

The kidney of male three-spined stickleback,Gasterosteus aculeatus, hypertrophies during the breeding season and produces a "glue" which is used in the building of the nest. This hypertrophy is androgen dependent, with 11-ketotestosterone (11KT) being more effective than other tested steroids in stimulating this secondary sexual character. In the present study kidneys were excised from stickleback males that had been castrated two days earlier. The purpose of this gonadectomy was to reduce the endogenous levels of androgens without allowing time for the kidney to regress. Tissue fragments were incubated with tritiated 11KT with and without unlabelled steroids at increasing concentrations. Displaceable specific 11KT binding was found in kidney tissue fragments whereas only non-specific binding was observed when liver and muscle were investigated in a similar way. Unlabelled 11KT displaced specifically bound, tritiated 11KT with an ED50-value (50% of displaceable binding) of 28 nM. Similar ED50 values were found for 17\-hydroxy-5α-androstane-3,11-dione (29 nM) and 5α-dihydrotestosterone (20 nM), whereas higher ED50 concentrations were estimated for testosterone (T; 203 nM) and progesterone (69 nM). No displacement of tritiated 11KT was found for the other investigated substances tested; estradiol, 17α,20β-dihydroxy-4-pregnen-3-one, flutamide or cyproterone acetate. No specific binding to kidney tissue fragments could be detected when labelled T was used instead of labelled 11KT. Specific binding of 11KT or T was not found either in the kidney cytosol or nuclear extracts. However, using the kidney membrane fraction a displacement of tritiated 11KT with unlabelled 11KT (10(-6)M) was observed. In conclusion there is a specific binding of 11KT in the stickleback kidney. The absence of binding in liver and muscle, the ED50 value observed and the displacement with some, but not all steroids are consistent with a receptor function. The presence of binding in membrane fractions, but not in cytosol or nuclear extracts suggests that the binding is not related to classic steroid receptors.

Incorporation of 3H-thymidine in the nephron of Gasterosteus aculeatus L. and its stimulation by methyltestosterone. A high-speed scintillation autoradiographic study

The rate of 3H-thymidine incorporation into different parts of the renal proximal tubule of female sticklebacks treated with methyltestosterone was investigated using high-speed scintillation autoradiography. The results are compared with those from normal males before or after mucous transformation of the kidney. Labelled cells are observed in all parts of the proximal tubule, with marked variations from one segment to another. They are numerous in part 2 of the proximal tubule, particularly in the distal region. Male sex hormones affect the labelling rate in all parts of the nephron, especially in the distal region of part 2 of the proximal tubule. In that particular area, new tubule formation by budding is observed in some individuals, but this process does not appear to be a general one. Correlation between the frequency of these figures and the time of treatment could not be established. Comparing the action of sex hormones in females with that in males reveals a difference in reactivity in the proximal zone of part 2 of the proximal tubule, where methyltestosterone has a strong action in females; in contrast, in "mature" and "immature" males, only a few labelled cells are present in this region. It is concluded that kidney enlargement during the breeding season does not result only from a swelling of cells belonging to part 2 of the proximal tubule, as was generally believed, but also from a lengthening or even a proliferation of the proximal tubules, induced by an increase in mitotic activity controlled by male sex hormones.