304
AUGUST EPPLE
Clarias lazeru, Yanni (1964) found a slight increase in muscle glycogen
and a slight decrease in liver glycogen, while insulin plus glucose increased
both muscle and liver glycogen. However, double dosage of insulin with
glucose had a similar effect to insulin alone, i.e., a strong increase in
muscle glycogen and a slight decrease in liver glycogen. Glucose administration without insulin caused the largest increase in both muscle
and liver glycogen. The glycogen content of several other tissues behaved
like the muscle glycogen under these experimental conditions. As in the
lamprey, the high glycogen content of the brain of Scorpaena decreased
after insulin injections (Plisetskaya, 1967). Thus, insulin may cause either
increase or decrease of liver glycogen, while muscle glycogen is either
unaffected or increased. In fishes with great glycogen storage in the brain
the latter is depleted.
c. Lipids. Apparently, there are no data available on the influence of
the islet hormones on the lipids in cyclostomes and elasmobranchs, although lipids seemingly play an extremely important role in these fishes
(cf. Bentley and Follett, 1965; Patent, 1 W ) . In teleosts, islectectomy
( McCormick and Macleod, 19%), B cell destruction by alloxan (La
Grutta, 1950), or exposure to a glucose-containing medium ( Kohler,
1963) increased the liver lipids. This could be prevented by application
of insulin. Insulin also decreased both liver and muscular lipids of both
normal and glucose- injected specimens of Clarias Zuzeru (Yanni, 1964).
In heart, liver, and muscle preparations of Opsunus tau there was no effect
of mammalian insulin on the in &To incorporation of glucose into total
lipids or fatty acids (Tashima and Cahill, 1964).
d. Proteins. In Ophicephalus striatus, insulin injections result hl a
decrease of muscle free amino acid and an increase of protein-bound
amino acids ( Seshadri, 1959).
The above observations, together with those given in Section 11, E, 1,
make it rather discouraging to draw conclusions on the physiological role
of insulin in fishes. There are many factors which possibly influenced the
results of the investigations such as species specificity of the hormone,
purity of the hormone (glucagon content), method of hormone application, dosage of the hormone, duration of the experiment, intervals between determinations, method of glucose or glycogen determinations,
handling and housing of the animals, nutritional state of the animals,
metabolic rate of the species, sex of the animals, season, water temperature, and various combinations thereof. With this in mind, it becomes
clear that many more data are necessary to evaluate the physiological
role of insulin. In future research, the use of species specific hormones as
AUGUST EPPLE
Clarias lazeru, Yanni (1964) found a slight increase in muscle glycogen
and a slight decrease in liver glycogen, while insulin plus glucose increased
both muscle and liver glycogen. However, double dosage of insulin with
glucose had a similar effect to insulin alone, i.e., a strong increase in
muscle glycogen and a slight decrease in liver glycogen. Glucose administration without insulin caused the largest increase in both muscle
and liver glycogen. The glycogen content of several other tissues behaved
like the muscle glycogen under these experimental conditions. As in the
lamprey, the high glycogen content of the brain of Scorpaena decreased
after insulin injections (Plisetskaya, 1967). Thus, insulin may cause either
increase or decrease of liver glycogen, while muscle glycogen is either
unaffected or increased. In fishes with great glycogen storage in the brain
the latter is depleted.
c. Lipids. Apparently, there are no data available on the influence of
the islet hormones on the lipids in cyclostomes and elasmobranchs, although lipids seemingly play an extremely important role in these fishes
(cf. Bentley and Follett, 1965; Patent, 1 W ) . In teleosts, islectectomy
( McCormick and Macleod, 19%), B cell destruction by alloxan (La
Grutta, 1950), or exposure to a glucose-containing medium ( Kohler,
1963) increased the liver lipids. This could be prevented by application
of insulin. Insulin also decreased both liver and muscular lipids of both
normal and glucose- injected specimens of Clarias Zuzeru (Yanni, 1964).
In heart, liver, and muscle preparations of Opsunus tau there was no effect
of mammalian insulin on the in &To incorporation of glucose into total
lipids or fatty acids (Tashima and Cahill, 1964).
d. Proteins. In Ophicephalus striatus, insulin injections result hl a
decrease of muscle free amino acid and an increase of protein-bound
amino acids ( Seshadri, 1959).
The above observations, together with those given in Section 11, E, 1,
make it rather discouraging to draw conclusions on the physiological role
of insulin in fishes. There are many factors which possibly influenced the
results of the investigations such as species specificity of the hormone,
purity of the hormone (glucagon content), method of hormone application, dosage of the hormone, duration of the experiment, intervals between determinations, method of glucose or glycogen determinations,
handling and housing of the animals, nutritional state of the animals,
metabolic rate of the species, sex of the animals, season, water temperature, and various combinations thereof. With this in mind, it becomes
clear that many more data are necessary to evaluate the physiological
role of insulin. In future research, the use of species specific hormones as