Decreased Tissue Guanylate Cyclase Activity in Glycosuric Djungarian Hamsters (Phodopus Sungorus) that is Correctable with Insulin

Summary

Twelve hyperglycemic, glycosuric, and ketonuric Djungarian hamsters with average blood glucose concentrations of 295 ± 32 mg/dl were compared to twelve non-glycosuric, but ketonuric Djungarian hamsters with average blood glucose concentrations of 88 ± 11 mg/dl with regards to their cyclic nucleotide metabolism. The glycosuric Djungarian hamsters had decreased guanylate cyclase (E.C.4.6.1.2.) activity in vitro and cyclic GMP levels in vivo in liver, lung, kidney, colon, heart, spleen, and pancreas that was approximately 50 % of the guanylate cyclase activity in these same tissues of non-glycosuric Djungarian hamsters. The decreased tissue guanylate cyclase activity and cyclic GMP levels in the glycosuric animals could be restored to the level of non-glycosuric Djungarian hamsters with 100 U regular insulin, but not with 50 or 10 U of regular insulin. Fifty and 100 U of regular insulin also increased the level of guanylate cyclase activity in the non-glycosuric (control) animals. There was no change in adenylate cyclase (E.C.4.6.1.1) activity but there were increased cyclic AMP levels in the glycosuric when compared to the non-glycosuric Djungarian hamsters that were correctable with 100 U of insulin. We conclude that guanylatecyclase activity is decreased in the peripheral tissues ofglycosuric Djungarian hamsters as compared to non-glycosuric Djungarian hamsters and that insulin modulates this enzyme.

Key-Words:

Spontaneously Hyperglycemic Djungarian hamsters - Guanylate Cyclse Activity - Cyclic AMP - Cyclic GMP - Insulin Sensitivity