6. ADRENAL STEROIDS AND ACTH
355
seem that in this preparation ACTH exerts its action via the adrenal
cortex.
VI. OTHER FACTORS AFFECTING ADRENOCORTICOSTEROID
LEVELS IN PLASMA
In certain teleost species such as the Pacific salmon and the rainbow
trout sexual maturation is accompanied by a marked hypertrophy of the
adrenal cortex (0. H. Robertson and Wexler, 1959; Hane and Robertson,
1959) and a sharp rise in circulating adrenal steroids (Idler et al., 1959b;
0. H. Robertson et al., 1961a; Schmidt and Idler, 1962; Donaldson and
Fagerlund, 1968). The biological half-life of injected cortisol also shows
a significant increase from 1.5 hr in the maturing salmon to 3.0 hr in the
spawned salmon (Idler and Truscott, 1963; Donaldson and Fagerlund,
1968). The volume of distribution is elevated in the spawned salmon, and
this more than offsets the decline in the observed fractional turnover rate.
From the data of Donaldson and Fagerlund, the secretory rate of cortisol
in the mature salmon is about 8 pg/lOo g body weightlday, while after
spawning it is increased to about 30 pg/lOO g/day. The possible implications of these changes in steroid metabolism and the breakdown of tissues
associated with sexual maturation of the gonads have been discussed in
Section 111, D.
The sequence of endocrine events associated with these changes in
metabolic clearances, secretory rates, and volumes of distribution are ill
defined, although factors other than the pituitary are probably involved.
In mammals, the adrenal cortex is influenced by the renin-angiotensin
system (see Ganong et al., 1966; Mulrow, 1966). The existence of renin
in teleost fishes is now well established, although the interplay between
renin, the adrenal cortex, and the kidney requires detailed investigation.
Friedman and associates obtained reninlike material from the kidneys of
freshwater fishes but failed to detect similar activity in the kidneys of
marine teleosts whether glomerular or aglomerular (Friedman and KapIan, 1942; Friedman et al., 1942).
The exact source of renin activity in teleost fishes is uncertain. Granular epithelioid cells have now been described in a large number of species (Edwards, 1941; McKelvey, 1963; Bohle and Walwig, 1964; Bulger
and Trump, 1965; Meyer et al., 1967; Capreol and Sutherland, 1968;
Lagios, 1968). These cells have a sporadic occurrence in some species
(Capreol and Sutherland, 1968) and in many instances extend some distances away from the glomerulus (Lagios, 1968). The histology of the
355
seem that in this preparation ACTH exerts its action via the adrenal
cortex.
VI. OTHER FACTORS AFFECTING ADRENOCORTICOSTEROID
LEVELS IN PLASMA
In certain teleost species such as the Pacific salmon and the rainbow
trout sexual maturation is accompanied by a marked hypertrophy of the
adrenal cortex (0. H. Robertson and Wexler, 1959; Hane and Robertson,
1959) and a sharp rise in circulating adrenal steroids (Idler et al., 1959b;
0. H. Robertson et al., 1961a; Schmidt and Idler, 1962; Donaldson and
Fagerlund, 1968). The biological half-life of injected cortisol also shows
a significant increase from 1.5 hr in the maturing salmon to 3.0 hr in the
spawned salmon (Idler and Truscott, 1963; Donaldson and Fagerlund,
1968). The volume of distribution is elevated in the spawned salmon, and
this more than offsets the decline in the observed fractional turnover rate.
From the data of Donaldson and Fagerlund, the secretory rate of cortisol
in the mature salmon is about 8 pg/lOo g body weightlday, while after
spawning it is increased to about 30 pg/lOO g/day. The possible implications of these changes in steroid metabolism and the breakdown of tissues
associated with sexual maturation of the gonads have been discussed in
Section 111, D.
The sequence of endocrine events associated with these changes in
metabolic clearances, secretory rates, and volumes of distribution are ill
defined, although factors other than the pituitary are probably involved.
In mammals, the adrenal cortex is influenced by the renin-angiotensin
system (see Ganong et al., 1966; Mulrow, 1966). The existence of renin
in teleost fishes is now well established, although the interplay between
renin, the adrenal cortex, and the kidney requires detailed investigation.
Friedman and associates obtained reninlike material from the kidneys of
freshwater fishes but failed to detect similar activity in the kidneys of
marine teleosts whether glomerular or aglomerular (Friedman and KapIan, 1942; Friedman et al., 1942).
The exact source of renin activity in teleost fishes is uncertain. Granular epithelioid cells have now been described in a large number of species (Edwards, 1941; McKelvey, 1963; Bohle and Walwig, 1964; Bulger
and Trump, 1965; Meyer et al., 1967; Capreol and Sutherland, 1968;
Lagios, 1968). These cells have a sporadic occurrence in some species
(Capreol and Sutherland, 1968) and in many instances extend some distances away from the glomerulus (Lagios, 1968). The histology of the