Abstract
It has been known for sometime that adult/neonatal rat and fetal rabbit brain contain an insulin-like substance whose precise identity, however, has remained in doubt. In an effort to clarify this issue, fetal rabbit brains (22-25-27d gestation; term~31d) were collected and either sliced for peroxidase-antiperoxidase (PAP) staining or extracted with an acid ethanol for SDS-PA gel and ELISA determinations. The monoclonal antibody used for PAP and ELISA analyses recognized insulin but not IGF-I.
Brain slices stained by the PAP technique for insulin showed no reactive cells despite using antibody concentrations as high as 1:20 (pancreatic islets were positive at 1:10,000 dilution). On the other hand, iodinated brain proteins separated by SDS-PAGE and located by autoradiography revealed a protein band that co-migrated with authentic porcine insulin (Mr~6000). In addition, ELISA analysis demonstrated the presence of ∼100ng of insulin per mg brain extract or 20g wet brain. This level of insulin was constant throughout the stages of fetal life studied. Why the peptide could not be detected by PAP staining remains unknown but might result from the presence of low amounts of antigen, antigen “masking” or antigen denaturation. We conclude that insulin is present in the fetal brain but in relatively minute amounts. The biologic function of the peptide within the brain remains to be studied.
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Schechter, R., Karycki, L., Kahn, A. et al. IDENTIFICATION AND QUANTITATION OF INSULIN IN THE FETAL RABBIT BRAIN. Pediatr Res 21 (Suppl 4), 254 (1987). https://doi.org/10.1203/00006450-198704010-00519
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DOI: https://doi.org/10.1203/00006450-198704010-00519