Constitutive nitric oxide synthase (cNOS) activity in Langerhans islets from streptozotocin diabetic rats

Brazilian Journal of Medical and Biological Research

T.m. Fonovich De Schroeder¹  M.d. Carattino¹  M. Frontera¹  O.l. Catanzaro¹ 

[1] ,Universidad de Buenos Aires

关键词: nitric oxide synthase;    nitric oxide;    Langerhans islets;    streptozotocin;    diabetes;   

DOI  :  10.1590/S0100-879X1998000500004

来源: SciELO

【 摘 要 】

Nitric oxide synthase activity was measured in Langerhans islets isolated from control and streptozotocin diabetic rats. The activity of the enzyme was linear up to 150 µg of protein from control rats and was optimal at 0.1 µM calcium, when it was measured after 45 min of incubation at 37oC in the presence of 200 µM arginine. Specific activity of the enzyme was 25 x 10-4 nmol [3H]citrulline 45 min-1 mg protein-1. Streptozotocin diabetic rats exhibited less enzyme activity both in total pancreas homogenate and in isolated Langerhans islets when compared to control animals. Nitric oxide synthase activity measured in control and diabetic rats 15 days after the last streptozotocin injection in the second group of animals corresponded only to a constitutive enzyme since it was not inhibited by aminoguanidine in any of the mentioned groups. Hyperglycemia in diabetic rats may be the consequence of impaired insulin release caused at least in part by reduced positive modulation mediated by constitutive nitric oxide synthase activity, which was dramatically reduced in islets severely damaged after streptozotocin treatment.

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