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

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Abstract
Twelve hyperglycemic, glycosuric and ketonuric Djungarian hamsters with average blood glucose concentrations of 295 .+-. 32 mg/dl were compared to 12 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 (EC 4.6.1.2.) activity in vitro and cGMP levels in vivo in liver, lung, kidney, colon, heart, spleen and pancreas that was .apprx. 50% of the guanylate cyclase activity in these same tissues of non-glycosuric Djungarian hamsters. The decreased tissue guanylate cyclase activity and cGMP 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 (EC 4.6.1.1) activity but there were increased cAMP levels in the glycosuric when compared to the non-glycosuric Djungarian hamsters that were correctable with 100 U of insulin. Guanylate cyclase activity apparently is decreased in the peripheral tissues of glycosuric Djungarian hamsters as compared to non-glycosuric Djungarian hamsters and insulin modulates this enzyme.