Summary
In sand rats high caloric food intake leads to hyperinsulinism, hyperglycemia, impaired
insulin action on glucose metabolism in muscle and adipose tissue as well as to reduced
hormone sensitive lipolysis associated with high circulating triglycerides and FFA-levels.
Some of our results concerning glucose metabolism in muscle have already implicated
that high epinephrine activity could contribute to the development of these metabolic
disturbances. To clarify this question we have taken the adrenodemedullated sand rat
as a model. Body weight, plasma insulin and glucose levels of adrenodemedullated sand
rats and of a control group of sham-operated animals were checked over 3 months after
operation. Thereafter the animals were decapitated and the hormone sensitivity of
adenylate cyclase in adipose tissue as well as of cAMP secretion was examined.
Epinephrine in the circulation of the adrenodemedullated sand rats was not detectable,
whereas in sham-operated animals its level was 0.99 ± 0.19 ng/ml. The norepinephrine
level in adrenodemedullated animals amounted to 0.84 ± 0.22 ng/ml, thus being definitely
lower than that of the controls (2.64±0.32 ng/ml). During the first 5 post-operative
weeks the body weight differed between the two groups, but thereafter it was practically
the same. Adrenal medullectomy prevented the development of hyperglycemia and significantly
reduced the degree of hyperinsulinism. The norepinephrine action on adenylate cyclase
activity of adipose tissue was significantly enhanced, and the insulin action on cAMP
release was only slightly affected when the adrenal medulla was resected. In comparable
experiments with young Wistar rats blood glucose and IRI-levels as well as norepinephrine
and insulin action on adenylate cyclase activity and cAMP secretion were not significantly
influenced by adrenal medullectomy. Our results support the significance of adrenergic
activity for the excessive level of plasma insulin and the development of hyperglycemia
in sand rats on a high caloric diet.
Key-Words:
Sand Rat
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Adrenal Medullectomy
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Sham Operated Animals
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Hyperglycemia
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Hyperinsulinism
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Adipose Tissue