3. FISH PROLACTIN AND GROWTH HORMONE
213
a relative impermeability of the body surface (particularly the gills) to
water. This hypothesis runs counter to Stanley and Fleming’s suggestion
(1967a) that in Fundulus kamae prolactin acts in both seawater and
freshwater to increase the water permeability of the integument.
Another role for paralactin in the eel, and one that would explain
Olivereau and Chartier-Baraduc’s results, is suggested by the ihdings
that hypophysectomy of freshwater eels leads to an increased outflux of
sodium from the body, which is corrected by ovine prolactin (Maetz et
al., 1967a). The failure of Chan et al. (1968) to alter plasma sodium
values in the eel with bovine prolactin may lie in the fact that sodium
outflux is of minor importance relative to the total electrolyte economy
of the eel, and it is this component alone that is influenced by prolactin,
Another point is that bovine prolactin appears to be less effective than
the ovine hormone in sodium conservation in P. latipinnu, and in inducing
freshwater survival in F . heteroclitus (Pickford et al., 1%), comparing
pigeon crop units of the two preparations; and in the work on the eel the
French workers used ovine prolactin while Chan et al. used bovine prolactin. At any rate, the eel offers an example of a teleost in which hypophysectomy does not abolish freshwater tolerance, but in which, nevertheless,the operation entrains some disturbance in mineral metabolism which
can be partially corrected by prolactin. Adrenocorticotropic hormone and
corticosteroids appear to be more important than paralactin in freshwater
osmoregulation in this species ( Chan et al., 1968,1969).
The goldfish, Carassius auratus, is another teleost which survives for
long periods in freshwater after hypophysectomy (Chavin, 1956) ; nevertheless, 3 weeks after the operation, goldfish in freshwater have very low
plasma levels of sodium and chloride, which apparently results from enhanced extrarenal loss of ions (probably across the gdls), renal sodium
loss being unaltered by hypophysectomy ( Lahlou and Sawyer, 1967).
Correspondingly, hypophysectomized goldfish on being transferred from
saline to freshwater displayed a lower than normal plasma osmolarity, and
this defect could be corrected by pretreatment with ovine prolactin or
with salmon acid-acetone-extracted pituitary powder ( Donaldson et al.,
1968); presumably in this case, as in F. heteroclitus and P. htipinnu
(below), the prolactin acted to limit the enhanced sodium outflux of the
hypophysectomized fish.
The eel and the goldfish appear to be able to live in freshwater after
hypophysectomy because of two rather different factors. In the eel the
prolactin-activated restriction of sodium outflux is of only minor importance to the animal compared with other, perhaps largely nonendocrine
mechanisms that operate when it moves to freshwater (Motais et al.,
1966; Maetz et al., 1967a; Chan et al., 1968), whereas in the goldfish, in
213
a relative impermeability of the body surface (particularly the gills) to
water. This hypothesis runs counter to Stanley and Fleming’s suggestion
(1967a) that in Fundulus kamae prolactin acts in both seawater and
freshwater to increase the water permeability of the integument.
Another role for paralactin in the eel, and one that would explain
Olivereau and Chartier-Baraduc’s results, is suggested by the ihdings
that hypophysectomy of freshwater eels leads to an increased outflux of
sodium from the body, which is corrected by ovine prolactin (Maetz et
al., 1967a). The failure of Chan et al. (1968) to alter plasma sodium
values in the eel with bovine prolactin may lie in the fact that sodium
outflux is of minor importance relative to the total electrolyte economy
of the eel, and it is this component alone that is influenced by prolactin,
Another point is that bovine prolactin appears to be less effective than
the ovine hormone in sodium conservation in P. latipinnu, and in inducing
freshwater survival in F . heteroclitus (Pickford et al., 1%), comparing
pigeon crop units of the two preparations; and in the work on the eel the
French workers used ovine prolactin while Chan et al. used bovine prolactin. At any rate, the eel offers an example of a teleost in which hypophysectomy does not abolish freshwater tolerance, but in which, nevertheless,the operation entrains some disturbance in mineral metabolism which
can be partially corrected by prolactin. Adrenocorticotropic hormone and
corticosteroids appear to be more important than paralactin in freshwater
osmoregulation in this species ( Chan et al., 1968,1969).
The goldfish, Carassius auratus, is another teleost which survives for
long periods in freshwater after hypophysectomy (Chavin, 1956) ; nevertheless, 3 weeks after the operation, goldfish in freshwater have very low
plasma levels of sodium and chloride, which apparently results from enhanced extrarenal loss of ions (probably across the gdls), renal sodium
loss being unaltered by hypophysectomy ( Lahlou and Sawyer, 1967).
Correspondingly, hypophysectomized goldfish on being transferred from
saline to freshwater displayed a lower than normal plasma osmolarity, and
this defect could be corrected by pretreatment with ovine prolactin or
with salmon acid-acetone-extracted pituitary powder ( Donaldson et al.,
1968); presumably in this case, as in F. heteroclitus and P. htipinnu
(below), the prolactin acted to limit the enhanced sodium outflux of the
hypophysectomized fish.
The eel and the goldfish appear to be able to live in freshwater after
hypophysectomy because of two rather different factors. In the eel the
prolactin-activated restriction of sodium outflux is of only minor importance to the animal compared with other, perhaps largely nonendocrine
mechanisms that operate when it moves to freshwater (Motais et al.,
1966; Maetz et al., 1967a; Chan et al., 1968), whereas in the goldfish, in