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Search for other papers by G. B. SANGALANG in
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SUMMARY
This report presents direct evidence for steroidogenesis by chondrostean tissue. The enzymes necessary for steroid transformation and cleavage of the cholesterol sidechain are present in yellow bodies isolated from the kidneys and along the posterior cardinal veins of the Atlantic sturgeon, Acipenser oxyrhynchus Mitchill.
Yellow bodies of the Atlantic sturgeon were incubated with [16-3H]pregnenolone plus [4-14C]progesterone in vitro and cortisol was formed in yields of 54·3 and 55·1% of the 3H and 14C precursor activities, respectively. Double-labelled cortisone, corticosterone, 11-deoxycortisol, 17α-hydroxyprogesterone and progesterone were isolated as transformation products but in relatively much lower yields. 11-Deoxycorticosterone, aldosterone and 1α-hydroxycorticosterone were not detected. When yellow bodies were incubated with [7-3H]cholesterol the following labelled transformation products were isolated: pregnenolone (0·43%), progesterone (0·091%), 17α-hydroxyprogesterone (0·023%), cortisol (0·061%), cortisone (0·004%), corticosterone (0·001%) and 11-deoxycortisol (0·047%). Again, 11-deoxycorticosterone, aldosterone, and 1α-hydroxycorticosterone were not detectable. All steroid products were identified by their isopolarity with authentic steroids by repeated chromatography, and by recrystallizations of free steroids and/or derivatives, after addition of authentic radio-inert steroids, to constant 3H:14C isotope ratios.
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Search for other papers by D. R. IDLER in
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SUMMARY
Cortisol was the principal steroid biotransformed from [16-3H]pregnenolone incubated with interrenal tissues of the Atlantic herring, Clupea harengus harengus, and of the Atlantic salmon, Salmo salar. Corticosterone was the preferred product from [4-14C]progesterone in herring, and cortisol in salmon. In these two teleosts 3H:14C recrystallization ratios of cortisol produced from the equimolar amounts of precursors at various times of incubation suggested that pregnenolone was the better precursor of cortisol and that the favoured pathway to cortisol was via 17-hydroxylated rather than 17-deoxy intermediates.
It was demonstrated that interrenal tissues of herring and salmon both have the capacity to 17-hydroxylate corticosterone to cortisol; aldosterone was not detected in any of the interrenal incubates. The 17-hydroxylation of 11-deoxycorticosterone to 11-deoxycortisol was shown in vitro by interrenal tissues of the Atlantic salmon, a conversion that has not been previously demonstrated in fish or in normal tissues of other vertebrates. When interrenal tissue of Atlantic salmon was incubated with equimolar amounts of [1,2-3H] 11-deoxycorticosterone plus [4-14C]corticosterone, there was more conversion of 11-deoxycorticosterone to 11-deoxycortisol (0·39%) than of corticosterone to cortisol (0·12%) and only a small amount (1·0%) of the 3H-labelled precursor was associated with corticosterone after 4 h incubation.
Biotransformed cortisol was isolated from both herring and salmon interrenals incubated with each of the following pairs of equimolar substrates: [3H]21-deoxycortisol plus [4-14C]11-deoxycortisol, [3H]21-deoxycortisol plus [4-14C]corticosterone, and [7-3H]11-deoxycortisol plus [4-14C]corticosterone. Isotope ratios of product cortisol suggested that, under the in-vitro conditions employed, substrate efficiency to cortisol synthesis was in the order: 11-deoxycortisol ⪢ 21-deoxycortisol > corticosterone. The results indicated that steroid hydroxylations at C-11, C-17 and C-21 could occur in any order in vitro in interrenals of herring and of salmon.
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Search for other papers by M. WEISBART in
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Search for other papers by D. R. IDLER in
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SUMMARY
Double isotope derivative assays were used to determine the presence or absence of testosterone, cortisol, cortisone, corticosterone, 11-deoxycortisol and 11-deoxycorticosterone in plasma samples from two (one sexually immature and one sexually mature) male American Atlantic sturgeon, Acipenser oxyrhynchus Mitchill. Submicrogram levels of testosterone were detected in the dichloromethane-extractable ('free' steroid) fractions of the plasma samples from both the immature and the mature fish; the level was much higher in the plasma of the mature fish. Very low levels of 'free' cortisol, cortisone and corticosterone were also detected in the plasma of the immature fish. The presence of 11-deoxycorticosterone and 11-deoxycortisol could not be firmly established in any of the samples. Preliminary analysis for conjugated testosterone in the plasma of the immature fish failed to show any detectable enzyme-released testosterone.
