6. ADRENAL STEROIDS AND ACTH
345
In concluding this section it is clear that much data have been accumulated on the effects of adrenalectomy on the osmoregulatory processes of the eel. Since this operation is a very drastic one, involving as it
does removal of part of the head kidney, both anterior cardinal veins, the
left posterior cardinal vein, and replacing the right posterior cardinal vein
with an artificial cannula (Chester Jones et al., lW), one must ask the
question whether the disruption of the circulation in this part of the animal is responsible for some of the effects observed. One piece of evidence
against this is that in both freshwater- and seawater-adapted eels, injection of small doses of cortisol readily alleviate the deranged osmoregulatory processes which develop following adrenalectomy (D. K. 0. Chan
et al., 1969; Mayer et al., 1967). However, there is still the possibility
that adrenocortical hormones exert their effects via changes in the microcirculation of the target organ itself (Schayer, 1964). This aspect has not
yet been explored in the fish.
C. Effects of Pharmacological Induction of Adrenocortical Insufficiency
There have been several attempts to induce adrenocortical ins&ciency by pharmacological means. Thus amphenone B and metopirone
(Ciba SU 4885) inhibit 11- and 17-hydroxylations in most if not all vertebrates (Gaunt et al., 19%). However, these compounds will not inhibit
the biosynthesis of compounds such as 11-deoxycortisol. In fact there is
strong evidence that production of this compound is enhanced in animals
receiving metopirone. Moreover, metopirone has been reported to have
its own effects as well (Janssens, 1967). Aldactone and other spironolactones antagonize the action of aldosterone (Drill, 1962).
In the freshwater eel, injection of metopirone alone did not affect
plasma and muscle electrolyte concentrations. Metopirone is known to
cause feedback release of Dituitary ACTH which can be inhibited by
simultaneous administration of a p- or dexa-methasone. Injection of
metopirone together with p-methasone caused a decline in plasma sodium
concentration and a rise in muscle water and sodium content (D. K. 0.
Chan et al., 196%). However, metopirone can inhibit the net uptake of
sodium from the environmental water by the gills (Henderson and
Chester Jones, 1967). Aldactone had similar effects on branchial sodium
uptake in the freshwater eel (Henderson and Chester Jones, 1967) and
probably in the freshwater lamprey ( Bentley and Follet, 1962).
The secretory pattern of the teleostean adrenal cortex following administration of these various blockers and antagonists has not been investigated. The results must therefore be a direct extrapolation from
345
In concluding this section it is clear that much data have been accumulated on the effects of adrenalectomy on the osmoregulatory processes of the eel. Since this operation is a very drastic one, involving as it
does removal of part of the head kidney, both anterior cardinal veins, the
left posterior cardinal vein, and replacing the right posterior cardinal vein
with an artificial cannula (Chester Jones et al., lW), one must ask the
question whether the disruption of the circulation in this part of the animal is responsible for some of the effects observed. One piece of evidence
against this is that in both freshwater- and seawater-adapted eels, injection of small doses of cortisol readily alleviate the deranged osmoregulatory processes which develop following adrenalectomy (D. K. 0. Chan
et al., 1969; Mayer et al., 1967). However, there is still the possibility
that adrenocortical hormones exert their effects via changes in the microcirculation of the target organ itself (Schayer, 1964). This aspect has not
yet been explored in the fish.
C. Effects of Pharmacological Induction of Adrenocortical Insufficiency
There have been several attempts to induce adrenocortical ins&ciency by pharmacological means. Thus amphenone B and metopirone
(Ciba SU 4885) inhibit 11- and 17-hydroxylations in most if not all vertebrates (Gaunt et al., 19%). However, these compounds will not inhibit
the biosynthesis of compounds such as 11-deoxycortisol. In fact there is
strong evidence that production of this compound is enhanced in animals
receiving metopirone. Moreover, metopirone has been reported to have
its own effects as well (Janssens, 1967). Aldactone and other spironolactones antagonize the action of aldosterone (Drill, 1962).
In the freshwater eel, injection of metopirone alone did not affect
plasma and muscle electrolyte concentrations. Metopirone is known to
cause feedback release of Dituitary ACTH which can be inhibited by
simultaneous administration of a p- or dexa-methasone. Injection of
metopirone together with p-methasone caused a decline in plasma sodium
concentration and a rise in muscle water and sodium content (D. K. 0.
Chan et al., 196%). However, metopirone can inhibit the net uptake of
sodium from the environmental water by the gills (Henderson and
Chester Jones, 1967). Aldactone had similar effects on branchial sodium
uptake in the freshwater eel (Henderson and Chester Jones, 1967) and
probably in the freshwater lamprey ( Bentley and Follet, 1962).
The secretory pattern of the teleostean adrenal cortex following administration of these various blockers and antagonists has not been investigated. The results must therefore be a direct extrapolation from