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SUMMARY
Fluorescence analyses and observations of plasma extracts on thin-layer chromatoplates including sulphuric acid chromogens failed to indicate the high concentrations of cortisol and corticosterone in Atlantic hagfish and sea lamprey reported by other workers. Double isotope derivative assays of Atlantic hagfish plasma and sea lamprey plasma failed to provide rigorous proof of the presence of these steroids.
Presumptive adrenocortical tissue from Atlantic hagfish and sea lamprey, incubated with radioactive steroids as precursors, failed to give any transformation to cortisol or corticosterone. However, sea lamprey incubations did produce 17α-hydroxyprogesterone from progesterone. No evidence was found for the presence of 17α-hydroxyprogesterone in microgram quantities in the plasma.
These findings are discussed in relation to previous studies in which high concentrations of cortisol and corticosterone were reported.
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ABSTRACT
Cortisol kinetics were examined in brook trout (Salvelinus fontinalis) to assess possible relationships with body fluid distribution during acclimation to sea water (SW). The disappearance curve of [3H]cortisol in plasma, after a bolus injection, was analysed by compartmental analysis using a three-pool mammillary model. The results indicated that only ∼ 10% of the total exchangeable cortisol was located in the plasma pool. Over 75% of the total cortisol was associated with a large slowly exchanging pool and the remaining cortisol was located in a second extravascular tissue pool which was in rapid exchange with the plasma pool.
Two days after transfer of trout from fresh water to SW, when plasma chloride concentration was at a new steady state, body weight, intracellular fluid volume, haematocrit and inulin clearance rate were lowered but plasma, blood and extracellular volumes were unaltered. Cortisol plasma clearance rate was unaltered but plasma cortisol concentration, cortisol secretion rate, total cortisol pool size and interpool transport rates were increased. These results are consistent with an acute role for cortisol in SW adaptation of brook trout.
The fraction of the total cortisol cleared was smaller and the average time that cortisol spent in the tissue pools was slightly longer in trout after transfer to SW, possibly reflecting altered fluid dynamics. The fractional disappearance rate was larger at higher plasma cortisol concentrations in the SW trout. This relationship is compatible with the hypothesis that cortisol protein binding protects cortisol from metabolism.
J. Endocr. (1985) 107, 57–69
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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.
