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J. N. BALL
plasma chloride (Burden, 1956) and total serum osmolality, the latter
being preventable by ovine prolactin (Pickford et al., 1966a). Similarly,
failing P. Zutipinna in freshwater display a fall in plasma sodium, but not
of potassium, which is corrected by a single injection of ovine prolactin
(Ball and Ensor, 1965, 1967). It is in the work on F. heteroclitus and P.
latipinnu that there is to be found the most considerable evidence for
regarding fish prolactin as a physiologically important part of the pituitary
equipment of teleosts. In evaluating the possible physiological significance
of the effect of a mammalian pituitary hormone on a teleost, a first
question must be whether the effect is specific, or if it can be produced
by other pituitary factors. Dr. Pickford and her collaborators have addressed themselves to this question in the case of the killifish, F. heteroclitus, and have shown in this fish that the ability to promote freshwater
survival after hypophysectomy is unique to prolactin; it is not shared by
thyroxine, ACTH, TSH, growth hormone, ACTH-TSH-growth hormone
combination, posterior lobe extract, arginine vasotocin, isotocin, urophyseal extracts, DOC, cortisol, aldosterone, corpuscles of Stannius extracts, hog renin, and parathyroid hormone. Effective substances were
ovine and bovine prolactins (the latter less effective than the former in
terms of its known pigeon crop activity), and two primate growth hormones (monkey and human) known to contain prolactin activity. Pituitary brei of rat, freshwater perch, and F. heteroclitus were effective, but
not homogenates or extracts of pituitaries from the marine pollack or the
freshwater carp (Burden, 1956; Pickford and Phillips, 1959; Pickford
et al., 1965). Furthermore, the 7 cells, source of fish prolactin ( see chapter
by Ball and Baker, Volume II), are very much more active and more
numerous in killifish adapted to freshwater than to seawater (Ball and
Pickford, 1964; Emmart et al., 1966), suggesting that fish prolactin really
is physiologically involved in maintaining the fish in freshwater, but it is
not so important in seawater [see also Schreibman and Kallman (1968)
and Dharmamba and Nishioka ( 19sS) 1.
Following the finding that ovine prolactin prevents the rapid fall in
plasma sodium in hypophysectomized P . latipinnu in freshwater (Ball and
Ensor, 1965), this action was shown to be a specific property of prolactin.
Ineffective hormones, each tested at a low and a high dose, were oxytocin,
vasopressin, arginine vasotocin, isotocin, ACTH, growth hormone, TSH,
and a-MSH. Gonadotropins were excluded, since natural or experimental
alterations in the pituitary-ovary axis were found not to affect survival in
freshwater (Ball and Ensor, 1967). The response to prolactin was dosedependent, and in a slightly modified protocol frog pituitary homogenates
produced a response paralleling that to ovine prolactin, indicating that the
presence of other hormones in the homogenates did not distort the effects
J. N. BALL
plasma chloride (Burden, 1956) and total serum osmolality, the latter
being preventable by ovine prolactin (Pickford et al., 1966a). Similarly,
failing P. Zutipinna in freshwater display a fall in plasma sodium, but not
of potassium, which is corrected by a single injection of ovine prolactin
(Ball and Ensor, 1965, 1967). It is in the work on F. heteroclitus and P.
latipinnu that there is to be found the most considerable evidence for
regarding fish prolactin as a physiologically important part of the pituitary
equipment of teleosts. In evaluating the possible physiological significance
of the effect of a mammalian pituitary hormone on a teleost, a first
question must be whether the effect is specific, or if it can be produced
by other pituitary factors. Dr. Pickford and her collaborators have addressed themselves to this question in the case of the killifish, F. heteroclitus, and have shown in this fish that the ability to promote freshwater
survival after hypophysectomy is unique to prolactin; it is not shared by
thyroxine, ACTH, TSH, growth hormone, ACTH-TSH-growth hormone
combination, posterior lobe extract, arginine vasotocin, isotocin, urophyseal extracts, DOC, cortisol, aldosterone, corpuscles of Stannius extracts, hog renin, and parathyroid hormone. Effective substances were
ovine and bovine prolactins (the latter less effective than the former in
terms of its known pigeon crop activity), and two primate growth hormones (monkey and human) known to contain prolactin activity. Pituitary brei of rat, freshwater perch, and F. heteroclitus were effective, but
not homogenates or extracts of pituitaries from the marine pollack or the
freshwater carp (Burden, 1956; Pickford and Phillips, 1959; Pickford
et al., 1965). Furthermore, the 7 cells, source of fish prolactin ( see chapter
by Ball and Baker, Volume II), are very much more active and more
numerous in killifish adapted to freshwater than to seawater (Ball and
Pickford, 1964; Emmart et al., 1966), suggesting that fish prolactin really
is physiologically involved in maintaining the fish in freshwater, but it is
not so important in seawater [see also Schreibman and Kallman (1968)
and Dharmamba and Nishioka ( 19sS) 1.
Following the finding that ovine prolactin prevents the rapid fall in
plasma sodium in hypophysectomized P . latipinnu in freshwater (Ball and
Ensor, 1965), this action was shown to be a specific property of prolactin.
Ineffective hormones, each tested at a low and a high dose, were oxytocin,
vasopressin, arginine vasotocin, isotocin, ACTH, growth hormone, TSH,
and a-MSH. Gonadotropins were excluded, since natural or experimental
alterations in the pituitary-ovary axis were found not to affect survival in
freshwater (Ball and Ensor, 1967). The response to prolactin was dosedependent, and in a slightly modified protocol frog pituitary homogenates
produced a response paralleling that to ovine prolactin, indicating that the
presence of other hormones in the homogenates did not distort the effects