Decrease of nitric oxide synthase in the cerebrocortex of streptozotocin-induced diabetic rats

In an attempt to know the role of nitric oxide in the disease of insulin-de pendent diabetic mellitus (IDDM), the present study examined the change of nitric oxide synthase (NOS) both the activity and gene expression in cerebr ocortex of streptozotocin-induced diabetic rats (STZ-diabetic rats). The ac tivity of NOS determined by conversion of [H-3] L-arginine to [H-3] L-citru lline was markedly decreased in STZ-diabetic rats. Northern blot showed tha t STZ-diabetic rats expressed a lower mRNA level of neuronal NOS (nNOS). We stern blot showed a similar decrease of nNOS in STZ-diabetic rats. However, the NOS activity was increased in rats receiving repeated supply of glucos e named glucose-challenged rats. Although the mRNA level of nNOS was not ch anged in the glucose-challenged rats, the immunoblot of nNOS was also decre ased in glucose-challenged rats. These findings suggested that NOS was lowe red in the brain of STZ-diabetic rats in a way unrelated to the increase of glucose. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.