1-alpha-hydroxycorticosterone: synthesis in vitro and properties of an interrenal steroid in the blood of cartilaginous fish (genus Raja)

Measurement of 1α hydroxycorticosterone in the Japanese banded houndshark, Triakis scyllium, following exposure to a series of stressors

An endocrine glucocorticoid response following exposure to a stressor has been well described for many vertebrates. However, despite demonstration of secondary stress responses in a number of elasmobranchs, our understanding of the endocrine control of these responses is lacking. This is largely due to the unusual structure of the dominant corticosteroid in elasmobranch fish, 1α-hydroxycorticosterone (1α-OH-B). Here we describe plasma extraction and HPLC separation procedures that allowed for the measurement of 1α-OH-B and corticosterone from plasma samples in the cannulated, conscious free-swimming Japanese banded houndshark, Triakis scyllium. While patterns of concentration in the plasma for 1α-OH-B and corticosterone were found to be similar in all experiments conducted, circulating levels of 1α-OH-B were consistently 100-fold greater than circulating levels of corticosterone. Immediately following cannulation surgery, circulating levels of 1α-OH-B increased 7-fold compared to pre-surgery levels, while the levels were 11-fold higher than pre-stress levels 30 min post a repeated handling/air-exposure stress. A three week period of fasting resulted in a 22-fold increase in circulating levels of 1α-OH-B in the banded houndshark. This is the first report of direct measurement of changes in circulating levels of the primary corticosteroid in elasmobranch fish, 1α-OH-B, following exposure to a stressor such as handling/air-exposure. Data indicate the steroid may respond similarly to the classic glucocorticoid response, such as cortisol in teleosts.

Biosynthesis of 1α-hydroxycorticosterone in the winter skate Leucoraja ocellata: evidence to suggest a novel steroidogenic route

The present study explores the ability of intracellular bacteria within the renal-inter-renal tissue of the winter skate Leucoraja ocellata to metabolize steroids and contribute to the synthesis of the novel elasmobranch corticosteroid, 1α-hydroxycorticosterone (1α-OH-B). Despite the rarity of C1 hydroxylation noted in the original identification of 1α-OH-B, literature provides evidence for steroid C1 hydroxylation by micro-organisms. Eight ureolytic bacterial isolates were identified in the renal-inter-renal tissue of L. ocellata, the latter being the site of 1α-OH-B synthesis. From incubations of bacterial isolates with known amounts of potential 1α-OH-B precursors, one isolate UM008 of the genus Rhodococcus was seen to metabolize corticosteroids and produce novel products via HPLC analysis. Cations Zn²⁺ and Fe³⁺ altered metabolism of certain steroid precursors, suggesting inhibition of Rhodococcus steroid catabolism. Genome sequencing of UM008 identified strong sequence and structural homology to that of Rhodococcus erythropolis PR4. A complete enzymatic pathway for steroid-ring oxidation as documented within other Actinobacteria was identified within the UM008 genome. This study highlights the potential role of Rhodococcus bacteria in steroid metabolism and proposes a novel alternative pathway for 1α-OH-B synthesis, suggesting a unique form of mutualism between intracellular bacteria and their elasmobranch host.

Serum concentrations of steroid hormones in the mature male bonnethead shark, Sphyrna tiburo

The male bonnethead shark, Sphyrna tiburo, undergoes an annual cycle of spermatogenesis and testicular regression and recrudescence. In southwestern Florida populations, testicular development and spermatogenesis begin in late spring and peak in late summer, with mating not taking place until about 2 months after the peak. Steroid hormones, some of which are known to play influential, essential roles in spermatogenesis, were measured in the serum during a full annual cycle in mature males from a wild population. Serum 17beta-estradiol (E2), progesterone (P4), testosterone (T), and dihydrotestosterone (DHT) concentrations were determined by radioimmunoassay. Serum T, DHT, and P4 concentrations followed the pattern of testicular development and regression, with all three steroid hormones attaining the highest significant levels (P < 0. 001) in late summer and falling to the lowest levels in mid-winter. Serum E2 concentrations showed significant changes (P < 0.01) with a peak in early spring. Male bonnethead sharks had significantly lower concentrations of E2 (P < 0.001) and significantly higher concentrations of T, DHT (P < 0.001), and P4 (P < 0.05) than those published for females. When steroid concentrations were compared to a behavioral rating of stress, only P4 showed a significant correlation to the stress behavior (P = 0.0447), but the significance was much lower than the significant correlation of P4 by month (P < 0.001).

In vitro biosynthesis of 17 alpha,20 alpha,20 beta-dihydroxy-4-pegnen-3-one by the ovaries, testes, and head kidneys of the Atlantic salmon Salmo salar

Ovaries, testes, and head kidneys of sexually mature Atlantic salmon, Salmo salar, biosynthesized 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17 alpha,20 beta-diOHP) from equimolar amounts of [3H]pregnenolone plus [4-14C]progesterone in vitro. The 3H:14C isotope ratios of steroid metabolites indicated that the biosynthetic pathways to 17 alpha,20 beta-diOHP in the testes differed from those observed in the ovaries and head kidneys. [4-14C]Progesterone appeared to be the principal precursor of 17 alpha,20 beta-diOHP in the testes, whereas both precursors were efficiently biotransformed to 17 alpha,20 beta-diOPH in the ovaries and head kidneys. 17 alpha-Hydroxy-4-pregnen-3-one (17 alpha-OHP) was the immediate precursor to 17 alpha,20 beta-diOHP in all tissues. However, appreciable amounts of 17 alpha,20 beta-diOHP accumulated in vitro in the testes only in the presence of exogenous [14C]progesterone. Incubation of the testes, ovaries, and head kidneys with [14C]pregnenolone resulted in high yields of 17 alpha,20 beta-diOHP in the ovaries and head kidneys but no detectable amounts of the steroid in the testes. The results confirm that progesterone is the favored precursor to 17 alpha,20 beta-diOHP in the testes. The results also suggest that the head kidneys may be an excellent cellular source of 17 alpha,20 beta-diOHP in both male and female. Atlantic salmon and may play an important role in the sexual maturation process in this fish. It is suggested that biosynthetic control mechanism affecting 17 alpha,20 beta-diOHP synthesis and/or spermiation and ovulation may differ in male and female Atlantic salmon.

The effect of temperature on steroid biosynthesis by testes of the dogfish, Scyliorhinus caniculus

1. Testes of the dogfish, Scyliorhinus caniculus, were incubated with [3H]pregnenolone and [3H]testosterone at a range of temperatures from 1 to 36 degrees C. 2. Yields of testosterone from pregnenolone were maximal between 11 and 16 degrees C, corresponding to the breeding temperature of the species. 3. Yields of glucuronides and sulphates increased from 1 to 26 degrees C. 4. Yields of an unidentified polar metabolite increased with temperature and it is suggested that this may play a regulatory role in elasmobranch reproduction.

21-Hydroxypregna-1,4-diene-3,11,20-trione: a biliary metabolite of a cartilaginous fish, Raja sp

21-Hydroxypregna-1,4-diene-3,11,20-trione was isolated from skate bile and as an in vivo metabolite of 3H-1alpha-hydroxycorticosterone. Identity was established by chromatography and derivatization to constant 3H/14C ratio and mass spectrometry of the 20,21-acetonide. The new steroid was present in the free form and as the glucuronoside.

Interrenalectomy and Stress in Relation to Some Blood Components of an Elasmobranch (Raja radiata)

From the literature there was a doubt as to whether interrenalectomy would result in elevated plasma potassium levels in a elasmobranch; in this study, no elevation was observed by comparison with sham-operated thorny skate (Raja radiata) held in sea water for up to 44 days post-operative.Blood calcium levels were significantly elevated in the interrenalectomized animals between 13 and 23 days but the increase was only 10%.There was no change in osmolality, sodium chloride, magnesium, or urea which can be attributed to interrenalectomy. Noteworthy was the manner in which both sham and interrenalectomized animals were able to maintain plasma electrolyte levels during the long period of starvation after surgery. Whenever significant changes occurred during the course of the experiment, sham and interrenalectomized fish were similarly affected, apart from the exception noted for calcium.Plasma urea levels were significantly depressed after interrenalectomy when the skates were held in a 3:1 mixture of sea water: fresh water for 7–9 days. The same trend was observed for sham-operated animals but the decrease was not significant. Normal animals maintained plasma urea in 75% sea water but not in 60% sea water.

The partial characterization of 1-oxygenated steroids from urine of a hypertensive newborn child

1. Four substances from the urine of a hypertensive newborn girl were partially characterized and shown to be 17alpha-hydroxy-5beta-pregnane-1,3,20-trione, 3alpha,17alpha-dihydroxy-5beta-pregnane-1,20-dione, 3alpha,17alpha,20alpha-trihydroxy-5beta-pregnan-1-one and 5beta-pregnane-1beta,3alpha,17alpha,20alpha-tetrol. 2. The characterization rested mainly on R(M) analysis of the substances and their derivatives by glycol fission, providing evidence for position and degree of substitution and for steroidal character. Supporting evidence was provided by chemically specific location reactions. 3. Certain problems in the manipulation of these beta-disubstituted steroids are discussed.

Hormones and endocrine glands of fishes. Studies of fish endocrinology reveal major physiologic and evolutionary problems

The structures discussed above illustrate some of the evolutionary knowledge to be obtained from studies of the comparative biology of the endocrine system among the fishes (see also 17, 78). The interrenal (adrenocortical) gland is an example of an endocrine structure which shows great morphologic variation in the vertebrate series, and among the fishes themselves. The structural variability implies little selective value for any particular pattern, and, in fact, biochemically the interrenal tissue would seem to be involved in much the same kind of steroidogenesis in the vertebrates generally. However, the hormone aldosterone may be a tetrapod novelty. The caudal neurosecretory system is a good example of a ubiquitous endocrine apparatus, among at least teleostean and elasmo-branch fishes, for which a function has yet to be elucidated and which continues to challenge the comparative physiologist. This system, along with the Stannius corpuscles, is lacking in the tetrapods. The existence of these structures makes it clear that the endocrine biology of fishes cannot be tacitly summarized as being essentially similar to that of the tetrapods, only less well developed. The prolactin situation illustrates the existence of a gland-the pituitary-present among fishes as among tetrapods, which secretes a product only partly related to the tetrapod hormone and having a very different functional significance. In this case it is clear that "the hormone and the uses to which it is put" have undergone evolutionary change during vertebrate phylogeny.