Three studies were conducted to evaluate the relationship between
insulin and nutritional parameters in rainbow trout. In the first study
effects on growth parameters and tissue composition of rainbow trout were
investigated following injection of bovine insulin at two dose levels
every 48 hr for 56 days. In addition, [¹⁴C]-leucine incorporation into
plasma, liver, and skeletal muscle was studied for the two insulin treatments
and a group of the saline-injected controls given a single shock-dose
of insulin (5.0 IU/kg). Hypoglycemic responses were observed with
all insulin treatments. In comparison to controls, high insulin treatment
gave a significant body weight increase. At both levels, insulin increased the content of protein, lipid, and also the incorporation of [¹⁴C]-leucine activity in skeletal muscle. Simultaneous decreases in specific
activity of plasma and liver tissue indicated a net movement of [¹⁴C]-leucine toward the peripheral musculature. No effect of the hormone was
seen on the glycogen content of liver or muscle tissue over the 56-day
period.
In a second study, the effect of bovine insulin on tissue incorporation of [¹⁴C]-glucose and [³H]-leucine was investigated in fed and fasted
rainbow trout reared on a control and high-protein diet. Insulin produced
marked hypoglycemia and mobilization of liver glycogen in all treatments.
Although insulin gave no evidence of glycogenic stimulation it
did appear to promote oxidative clearance of [¹⁴C]-glucose. Compared to
[¹⁴C]-glucose much greater tissue incorporation of [³H]-leucine was
observed in fasted fish; insulin stimulated the incorporation of [³H]-leucine into skeletal muscle protein. In plasma, liver, and skeletal
muscle of all treatments, the summed specific activities of [³H]-leucine
was considerably greater than that of the summed values of [¹⁴C]-glucose
following insulin administration. Four weeks of fasting apparently
lowered basal metabolism but no changes were observed in plasma glucose
and glycogen stores. There was some evidence of gluconeogenic activity
in the high protein-fasted fish and the data indicated in all fasted
treatments a stimulation of [¹⁴C]-glucose and [³H]-leucine metabolism
following insulin administration.
As a third investigation, [¹²⁵I]-iodoinsulin binding studies in
the presence of a concentration range of bovine insulin were conducted
to establish specific insulin binding levels in erythrocytes, skeletal
muscle plasma membranes and isolated hepatocytes of rainbow trout
reared on control-, high-protein and high-carbohydrate diets. Negative
cooperativity was observed and receptor concentrations and apparent
dissociation constants established for each preparation. No differences
of specific binding attributed to diet were detected in either erythrocytes
or skeletal muscle plasma membrane preparations, However, the
receptor concentration of isolated hepatocytes from high-carbohydrate
reared trout was increased. This contrasted to comparable mammalian
studies. In view of an apparent depression of receptor concentration in
skeletal muscle plasma membranes and isolated hepatocytes of high-protein
reared trout, these data were interpreted according to the
reciprocal relationship observed between endogenous insulin and insulin
receptor concentrations established for mammals. Unlike mammals where
glucose was shown to be the primary insulin secretagogue, endogenous
insulin levels in rainbow trout have been closely correlated to circulatory
amino acids and are thought to be primarily controlled by these
protein metabolites. / Graduation date: 1982
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27425 |
| Date | 24 November 1981 |
| Creators | Ablett, Richard F. |
| Contributors | Selivonchick, D. P. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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