332
CHESTER JONES, CHAN, HENDERSON, AND BALL
tutes another possibility. All these problems have been recognized in
fishes. Some of them have been studied and will be discussed in detail.
It is the intention of this chapter to bring together some of these developments and to point out areas where knowledge is lacking or where
current issues require clarification and further investigation. Adrenocorticosteroids may be seen to act upon the following processes: osmoregulation; protein and carbohydrate metabolism; blood cell movement
from hematopoietic and lymphoid tissues; growth, regeneration, and antiinflammatory reactions.
B. Osmoregulation
In all vertebrates it appears that adrenocorticosteroids play an important role in the maintenance of water and electrolyte homeostasis. Among
fishes a variety of osmoregulatory mechanisms have evolved within the
different taxonomic groups.
Injection of adrenocorticosteroids into fish affects the electrolyte balance. The results obtained depend on the individual steroid, the dose
used, and the recipient animal species.
In the hagfish, Myxine glutinosa, adapted to 60% seawater daily injection of low doses (20 pg/day ) of aldosterone had no effect on the electrolyte composition of plasma and muscle, but higher doses (80 pg/day)
caused a decline in muscle sodium concentration. A similar loss of muscle
sodium was induced by DOC but not cortisone (Chester Jones et al.,
1982). In Lumpetra fluviatilis in freshwater, aldosterone reduced the rate
of overall loss of sodium from the animals (renal and extrarenal) compared with the controls, while aldactone, an aldosterone antagonist, increased this loss (Bentley and Follet, 1962). When the urine was collected
it was found that neither aldosterone nor cortisol altered urinary sodium
excretion while aldosterone reduced urine volume slightly and cortisol
decreased urinary potassium excretion ( Bentley and Follet, 1963).
In the lip shark, HemiscyZZium plagiosum, injection of cortisol or DOC
did not affect the electrolyte composition of the intact animal. Cortisol
and DOC both caused a decline in the rate of secretion by the rectal salt
gland. In the shark loaded with hypertonic saline, cortisol but not DOC
helped maintain a constant sodium concentration in the plasma, the excess
sodium being found in the muscle (D. K. 0. Chan et al., 1967a). The
interpretation of this result is difficult since cortisol does not appear to
be a natural hormone for this class of fish.
In teleost fish, injections of high doses (milligrams) of adrenocorticosteroids often cause effects which disturb electrolyte balance. In the
CHESTER JONES, CHAN, HENDERSON, AND BALL
tutes another possibility. All these problems have been recognized in
fishes. Some of them have been studied and will be discussed in detail.
It is the intention of this chapter to bring together some of these developments and to point out areas where knowledge is lacking or where
current issues require clarification and further investigation. Adrenocorticosteroids may be seen to act upon the following processes: osmoregulation; protein and carbohydrate metabolism; blood cell movement
from hematopoietic and lymphoid tissues; growth, regeneration, and antiinflammatory reactions.
B. Osmoregulation
In all vertebrates it appears that adrenocorticosteroids play an important role in the maintenance of water and electrolyte homeostasis. Among
fishes a variety of osmoregulatory mechanisms have evolved within the
different taxonomic groups.
Injection of adrenocorticosteroids into fish affects the electrolyte balance. The results obtained depend on the individual steroid, the dose
used, and the recipient animal species.
In the hagfish, Myxine glutinosa, adapted to 60% seawater daily injection of low doses (20 pg/day ) of aldosterone had no effect on the electrolyte composition of plasma and muscle, but higher doses (80 pg/day)
caused a decline in muscle sodium concentration. A similar loss of muscle
sodium was induced by DOC but not cortisone (Chester Jones et al.,
1982). In Lumpetra fluviatilis in freshwater, aldosterone reduced the rate
of overall loss of sodium from the animals (renal and extrarenal) compared with the controls, while aldactone, an aldosterone antagonist, increased this loss (Bentley and Follet, 1962). When the urine was collected
it was found that neither aldosterone nor cortisol altered urinary sodium
excretion while aldosterone reduced urine volume slightly and cortisol
decreased urinary potassium excretion ( Bentley and Follet, 1963).
In the lip shark, HemiscyZZium plagiosum, injection of cortisol or DOC
did not affect the electrolyte composition of the intact animal. Cortisol
and DOC both caused a decline in the rate of secretion by the rectal salt
gland. In the shark loaded with hypertonic saline, cortisol but not DOC
helped maintain a constant sodium concentration in the plasma, the excess
sodium being found in the muscle (D. K. 0. Chan et al., 1967a). The
interpretation of this result is difficult since cortisol does not appear to
be a natural hormone for this class of fish.
In teleost fish, injections of high doses (milligrams) of adrenocorticosteroids often cause effects which disturb electrolyte balance. In the