Seasonal testosterone UDP-glucuronosyltransferase activity and biliary steroids in Eurasian perch: response to leachate exposure

In previous studies there was evidence of endocrine disruption in fish in waterways contaminated with leachate from a Swedish landfill. Symptoms included fewer sexually mature (SM) female perch (Perca fluviatilis), distinct sores, reduced gonadosomatic index, and decreased plasma androgen levels. Based on previous findings it was hypothesized that the decrease in plasma androgen concentrations could have been caused by increased steroid excretion. Therefore, testosterone UDP-glucuronosyl transferase (UDPGT) activity and biliary steroids were measured in SM and sexually immature (SIM) female perch during one reproductive cycle. UDPGT activity in exposed fish did not differ from reference fish and was similar in both SM and SIM female perch. Since androgen levels in SIM fish usually are much lower than in SM fish, this indicates expression of testosterone UDPGT irrespective of substrate availability. There was no general increase in biliary steroids in exposed female perch. Biliary steroid levels correlated with corresponding plasma steroid levels. In conclusion, the reduced androgen levels in exposed female perch are most likely not caused by increased steroid excretion.

Uptake and clearance of exogenous estradiol-17β and testosterone during the early development of coho salmon (Oncorhynchus kisutch), including eggs, alevins and fry

The uptake and clearance of estradiol-17β (E2) and testosterone (T) were examined during the initial stages of development of coho salmon (Oncorhynchus kisutch), including eyed-eggs, newly hatched alevins and first feeding fry. Radiolabeled steroids were administered through the water in tracer amounts with or without their nonradioactive form at 400 μg l(-1). Regardless of developmental stage, saturation levels were invariably attained earlier for T than for E2, thus resulting in a higher incorporation of E2. However, both steroids had similar clearance patterns. Uptake and clearance was clearly stage-dependent, being fastest in fry, intermediate in alevins and slowest in eggs. Furthermore, combined uptake and clearance patterns showed that exposure to steroid was also higher for E2 than for T and stage-dependent, but always markedly highest in alevins. Subsequently, based on the observed elimination of the estrogen, a double immersion in E2 at 400 μg 1(-1), administered 2 days apart to maximize exposure during the alevin stage, was assayed for its effect on sex reversal and found to induce the production of 100% females. We suggest that the yolk, which is present in substantial amounts during the initial stages of development in salmonids, can retain the exogenously administered liposoluble steroids, thus providing developing embryos with an extended supply of, and exposure to, these steroids well after the treatment is finished. Together, these findings help to explain the previously observed high effectiveness of sex steroids administered during early development in regulating gonadal differentiation in salmonids, the higher effectiveness of E2 compared to T, and clarify the localization of the most sensitive period to the action of exogenous steroids at the alevin stage in the coho salmon.

Plasma kinetics of ingested tritiated estradiol and the influence on estradiol plasma levels in the cultured Siberian sturgeonAcipenser baeri

Plasma kinetics of tritiated estradiol (E2) were studied in the Siberian sturgeonAcipenser baeri in order to explain the large amount of E2 found in plasma of 4, 5 and 10-year-old cultured males. This work presents two approaches. The first is based on a single ingestion of(3)H-labelled E2, which allowed us to plot model curves of resorption and elimination processes. The second deals with chronic ingestion of(3)H-labelled E2 during a five day period, twice a day, based on a rhythm copied from the feeding practice on a fish farm. Three different doses were tested, based on the amount present in fish diets. Oral administration of E2 to sturgeon leads to E2 accumulation and a saturation of the metabolic processes generally involved in the elimination of aromatic xenobiotics. An explanation of this progressive accumulation of E2 in sturgeon plasma has to take into account the steroid binding proteins. Their synthesis could be induced by the orally administrated E2 and protect it from metabolism.

Dosage-dependent differences in the effect of aromatizable and nonaromatizable androgens on the resulting phenotype of coho salmon (Oncorhynchus kisutch)

This study was conducted to investigate whether aromatization to estrogen could be the cause for the paradoxical feminization of gonads of sexually-undifferentiated fish after treatment with androgen at either high doses or for long periods. The aromatizable androgen 17α-methyltestosterone (MT) and the nonaromatizable androgen 17α-methyldihydrotestosterone (MDHT) were administered to groups of newly hatched coho salmon (Oncorhynchus kisutch) in a single 2h immersion at concentrations ranging from 6.25 to 6,400µg/l. The effects of treatment were evaluated by determining the resultant proportion of males in each experimental group. The effects of steroid administration on the final mean weight, length and condition factor were also determined. An increase in all these three variables was observed in the groups treated with the higher doses of MT. Regarding the resultant sexual phenotype, the response to both androgens was similar at the majority of doses tested. However, at the highest dose, the proportion of females increased with respect to that of males for MT, but not for MDHT. Since the major difference between the two androgens tested is their capacity to be aromatized, it seems that aromatization to estrogen, rather than inhibition of the biosynthesis of endogenous androgen, may explain the paradoxical feminization encountered.

The metabolic clearance rate of estradiol-17 beta in rainbow trout, Salmo gairdneri R., estimated by both single injection and constant infusion methods: increase during oocyte maturation

A dual cannulation of free-swimming rainbow trout is used to estimate the metabolic clearance rate (MCR) of Estradiol-17 beta (E2-17 beta) by both single injection and constant infusion methods. It is shown that E2-17 beta MCR changes significantly during the progress of oogenesis, mainly at the end of the sexual cycle. The same changes in MCR and very similar values are found with both single injection and constant infusion methods: MCR is stable (28.8 ml/hr/kg) from the postovulation period (throughout endogenous vitellogenesis) to early exogenous vitellogenesis. It decreases significantly during advanced exogenous vitellogenesis (18.7 ml/hr/kg) and increases clearly at the onset of oocyte maturation (40.9 ml/hr/kg). A direct relationship between MCR and plasma E2-17 beta occurs: Plasma E2-17 beta levels increase (advanced exogenous vitellogenesis) when MCR decreases. Then estradiol decline takes place at the same time that MCR reaches its highest values (oocyte maturation). An increase in MCR is probably one event required to allow the establishment of an appropriate hormonal environment for oocyte maturation.

[Plasma levels, metabolic clearance rates, and rates of secretion of testosterone and estradiol-l7 beta in the silver eel (Anguilla anguilla L.)]

Testosterone (T) and 17 beta-estradiol (E2) plasma levels and metabolic clearance rates (MCR) were measured to investigate their ovarian production in immature silver eel. The dynamics of T and E2 metabolism were studied in catheterized eels using single injections of 0.2 to 0.5 microCi 3H-labeled steroid. The distribution volumes, biological half-life and MCR of nonconjugated tracers were calculated on the basis of a two-compartment model. At the end of the experiments, radioactivity was measured in different organs and tissues to localize the site of T and E2 catabolism. The volume of the inner compartment was 3.4% for T and E2. The outer compartment was larger for T (6.4%) than that for E2 (4.3%). The biological half-life was three to four times shorter for T (14.5 hr) than that for E2 (48.5 hr). The MCR for T (1.71 ml/kg body wt/hr) was higher than for E2 (0.51 ml/kg body wt/hr). Plasma levels were determined, using radioimmunoassay, on samples taken before injections of radiolabeled steroid. Free or protein-bound hormone levels were 0.12 and 0.31 ng/ml for T and E2, respectively. Conjugated T and E2 levels were, respectively, 0.13 and 0.23 ng/ml. Production rates were determined as the product of the MCR and the plasma concentration of the nonconjugated hormone. No significant differences were observed between the production rates of T and E2 (0.24 ng/kg body wt/hr). The liver was the principal site of metabolism for both hormones, which were excreted via the enterohepatic route. E2 injection gave rise to no metabolite in the plasma whereas after T injection a metabolite was produced, the concentration of which increased as a function of time. Its chromatographic properties were different from that of E2 or androstenedione, suggesting that no significant peripheral aromatization or 17-oxidoreduction occurs in the immature silver eel.

Steroid metabolism in fish. II. Testosterone metabolites in the bile of the marine winter flounder Pseudopleuronectes americanus and the freshwater Atlantic Salmon Salmo salar

Intraarterial injection of [3H]testosterone in the flounder Pseudopleuronectes americanus and the landlocked salmon Salmo salar resulted in the concentration of radioactive catabolites in the gall bladder bile. The catabolites were quantitatively conjugated with glucuronic acid. In flounder bile, three steroids, testosterone, 5 beta-dihydrotestosterone and 5 beta-androstane-3 alpha,17 beta-diol accounted for most of the radioactivity. Quantitatively the concentration of 5 beta-dihydrotestosterone usually exceeded that of the other two compounds. In salmon bile, 5 alpha-dihydrotestosterone was also present as a minor catabolite and the dihydrotestosterones accounted for approximately one-half the total radioactivity. In both species there was evidence for trace amounts of 5 beta-androstane-3 beta,17 beta-diol, 5 alpha-androstane-3 alpha,17 beta-diol, and 5 alpha-androstane-3 beta,17 beta-diol but no evidence for 5 beta- or 5 alpha-androstanolones, 4-androstene-3 alpha,17 beta-diol, or its 3 beta-epimer. There were no obvious sex-related differences in the composition of the biliary testosterone metabolites.

Effect of acute exposure to crude petroleum on some reproductive hormones in salmon and flounder

1. The concentration of total (free + conjugated) androgens in plasma of sexually mature male salmon and flounder was generally lower in oil-exposed fish. 2. Exposure to crude oil inhibited some testicular development of salmon during the final stages of maturation. 3. Oil exposure had no effect on levels of total plasmatic androgens or estradiol in male and female flounder during gonadal recrudescence. 4. Aryl hydrocarbon hydroxylase activity increased in liver and kidney of both species. 5. Sperm, collected from salmon exposed to oil, fertilized eggs from non-exposed females to produce normal alevins.