3. FISH PROLACTIN AND GROWTH HORMONE
225
growth hormone, and a physiological role for fish prolactin in hemotopoiesis is far from proven. In an earlier investigation Slicher (1961) had
obtained no effects of prolactin on erythrocytes or thrombocytes in hypophysectomized F. heteroclitus, but in one experiment out of two she
found that prolactin elevated the leukocyte count. This last effect has not
been duplicated in our work on Poeciliu.
Currently there is considerable interest in demonstrations of growth
promotion by prolactin in various vertebrates. Evidence exists of overlap
of properties between growth hormone and prolactin in various vertebrates, and in particular there are several demonstrations of growth promotion by exogenous prolactin in amphibians, reptiles, birds, and mammals (see Bern et al., 1967; Licht and Jones, 1967; Bates et al., 1962,
1964; review, Ball et al., 1965). Little information is available for teleosts,
perhaps partly because of the difficulty of providing the ideal conditions
necessary for experimental fish to exhibit vigorous growth. Prolactin has
never been found to promote growth in hypophysectomized F. heteroclitus (Pickford and Kosto, 1957; Pickford, 1967), and endogenous fish
prolactin and growth hormone are certainly separate factors in Poeciliu
( Ball, 1965a; Ball et al., 1965). Prolactin treatment of hypophysectomized
P. latipinnu has not induced any signficant growth in length, although
like TSH it somewhat alleviates the shrinkage of hypophysectomized fish
(Ball, 1968).
F. Extraction of Paralactin and Hypothalamic Control
There have been no published studies on the isolation and physicochemical properties of paralactin. Acid-acetone extraction of salmon
pituitaries yielded a fraction which probably contained fish prolactin, inasmuch as it opposed the drop in serum osmolarity when hypophysectomized goldfish were transferred to freshwater (Donaldson et al., 1968).
Application of a modified Bates and Riddle (1935) procedure to carp
pituitary material produced a fraction that was presumed to be fish prolactin, but which had no biological activity when tested on hypophysectomized F. heteroclitus (Pickford et al., 1965). Material from carp and
pollack, but prepared by different procedures, proved able to cross-react
in vitro with a rabbit antibody to ovine prolactin in precipitin tests (Emmart et al., 1966; Wilhelmi, personal communication).
In mammals, prolactin is the only pars distalis hormone which is secreted at a high rate when the gland is separated from the hypothalamus,
and prolactin is apparently under inhibitory control of the hypothalamus
in this group (Meites and Nicoll, 1966). In fish, the ectopically trans-
225
growth hormone, and a physiological role for fish prolactin in hemotopoiesis is far from proven. In an earlier investigation Slicher (1961) had
obtained no effects of prolactin on erythrocytes or thrombocytes in hypophysectomized F. heteroclitus, but in one experiment out of two she
found that prolactin elevated the leukocyte count. This last effect has not
been duplicated in our work on Poeciliu.
Currently there is considerable interest in demonstrations of growth
promotion by prolactin in various vertebrates. Evidence exists of overlap
of properties between growth hormone and prolactin in various vertebrates, and in particular there are several demonstrations of growth promotion by exogenous prolactin in amphibians, reptiles, birds, and mammals (see Bern et al., 1967; Licht and Jones, 1967; Bates et al., 1962,
1964; review, Ball et al., 1965). Little information is available for teleosts,
perhaps partly because of the difficulty of providing the ideal conditions
necessary for experimental fish to exhibit vigorous growth. Prolactin has
never been found to promote growth in hypophysectomized F. heteroclitus (Pickford and Kosto, 1957; Pickford, 1967), and endogenous fish
prolactin and growth hormone are certainly separate factors in Poeciliu
( Ball, 1965a; Ball et al., 1965). Prolactin treatment of hypophysectomized
P. latipinnu has not induced any signficant growth in length, although
like TSH it somewhat alleviates the shrinkage of hypophysectomized fish
(Ball, 1968).
F. Extraction of Paralactin and Hypothalamic Control
There have been no published studies on the isolation and physicochemical properties of paralactin. Acid-acetone extraction of salmon
pituitaries yielded a fraction which probably contained fish prolactin, inasmuch as it opposed the drop in serum osmolarity when hypophysectomized goldfish were transferred to freshwater (Donaldson et al., 1968).
Application of a modified Bates and Riddle (1935) procedure to carp
pituitary material produced a fraction that was presumed to be fish prolactin, but which had no biological activity when tested on hypophysectomized F. heteroclitus (Pickford et al., 1965). Material from carp and
pollack, but prepared by different procedures, proved able to cross-react
in vitro with a rabbit antibody to ovine prolactin in precipitin tests (Emmart et al., 1966; Wilhelmi, personal communication).
In mammals, prolactin is the only pars distalis hormone which is secreted at a high rate when the gland is separated from the hypothalamus,
and prolactin is apparently under inhibitory control of the hypothalamus
in this group (Meites and Nicoll, 1966). In fish, the ectopically trans-