PREPROINSULIN-I AND PREPROINSULIN-II MESSENGER-RNAS AND INSULIN ELECTRON-MICROSCOPIC IMMUNOREACTION ARE PRESENT WITHIN THE RAT FETAL NERVOUS-SYSTEM

Insulin-like substance has been found within the nervous system. In th e rat, preproinsulin II mRNA was shown within the brain and preproinsu lin I mRNA within the retina. The present study demonstrates the prese nce of preproinsulin mRNAs within the 15, 17 and 19 day gestational ag e fetal rat brain, spinal cord and dorsal root ganglia (DRG), employin g RNA template-specific polymerase chain reaction (RS-PCR), semi-neste d PCR and RNase protection assay. Preproinsulin I mRNA was present in the 17 and 19 day gestational age brain, spinal cord and DRG, and only in the brain of the 15 day gestational age brain. Preproinsulin II mR NA was present in all the gestational ages studied in the brain, spina l cord and DRG. The RS-PCR and the semi-nested PCR demonstrated produc ts that co-migrated with the pancreatic control. The semi-nested produ cts were characterized as preproinsulin I and II by restriction enzyme digestion and sequence. RNase protection assay using specific cRNA fo r preproinsulin I and II showed a band that co-migrated with pancreati c preproinsulin I and II mRNAs, and confirmed the PCR results. In addi tion, insulin receptor mRNA was detected by RS-PCR. Ultrastructural st udies showed insulin immunoreaction within the endoplasmic reticulum, Golgi apparatus, cytoplasm, axon, dendrites, and in relation to the sy napses. Thus, we demonstrated the presence of preproinsulin I and II m RNA, insulin receptor mRNA and insulin immunoreaction within the rat f etal central and peripheral nervous system.