Impaired Hormonal Regulation of Adenosine 3′,5′-Monophosphate Release in Adipose Tissue from Hyperglycemic Sand Rats In Vitro

Summary

Egyptian sand rats (Psammomys obesus) developed under laboratory holding conditions and in dependence of different food intake various states of hyperglycemia and hyperinsulinism.

Associated with the development of this syndrome insulin resistance of muscle- and adipose tissue appears.

The question arose as to whether hyperglycemia and hyperinsulinism generally leads to hormone resistance. Therefore, we selected sand rats with different degrees of hyperglycemia and various stages of hyperinsulinism.

Two groups of sand rats were investigated: normoglycemic and hyperglycemic animals. In these sand rats the catecholamine action on cAMP production by adipose tissue was studied in vitro. There was a significant reduction of hormone responsiveness in adipose tissue of the hyperglycemic group compared with the noradrenaline response of adipose tissue of the normoglycemic sand rats. In no case had insulin significantly inhibited the noradrenaline stimulated cAMP production.

By means of adenosine deaminase studies the interference of the eventual release of adenosine with the hormone action on adipose tissue in vitro could be excluded.

In the sand rats correlations between IRI levels in the decapitation blood and noradrenaline stimulated cAMP release associated with simultaneous occurrence of insulin- and catecholamine resistance in adipose tissue seem to indicate that hormone resistance could be a general phenomenon during the development of hyperinsulinism.

Key-Words:

Sand Rat - Hyperglycemia - Hyperinsulinism - Insulin Resistance - Catecholamine Resistance - cAMP Release - Adipose Tissue - Adenosine