DIABETES-INDUCED SUPPRESSION OF IGF-1 AND ITS RECEPTOR MESSENGER-RNA LEVELS IN RAT SUPERIOR CERVICAL-GANGLIA

Insulin-like growth factor-I (IGF-I) is implicated in the development: survival and maintenance of function of sympathetic and sensory neuro ns. These neurons are affected at an early stage during the course of diabetes, Reverse transcriptase polymerase chain reaction (RT-PCR) bas ed assay revealed that rat superior cervical ganglia (SCG) express mRN A transcripts for IGF-I and its receptor. Moreover, specific membrane protein binding sites for IGF-I within the SCG have also been demonstr ated using competition-inhibition and affinity cross-linking technique s. An induction of diabetes with streptozotocin (STZ, 55 mg/kg, i.v.) produced a marked decrease in the SCG levels of mRNA transcripts for I GF-I and its receptor. Concentrations of circulating IGF-I and its rec eptor protein within the SCG were also reduced in this disease state. Insulin treatment partially prevented diabetes-related alterations in circulating IGF-I and the SCG-IGF-I system. Overall, the data describe d in this study may be of value in understanding the pathogenetic mech anism(s) responsible for the development of diabetic sympathetic neuro pathy. (C) 1997 Elsevier Science Ireland Ltd.