Proinsulin in B Cells of Bovine Islets Demonstrated by Fluorescein or Peroxidase-Labeled Specific Antibody

Sera of guinea pigs immunized with crude bovine proinsulin, and adsorbed with a solid Sephadex-insulin immunosorbent, yielded highly specific antibodies against proinsulin.

Positive immunoreaction was obtained in the β cells of fetal and adult bovine islets with the specific antiproinsulin antibody preparations in the Coons' direct and indirect method with fluorescein- or peroxidase-labeled antibodies. It is concluded that proinsulin and/or other antigens bearing the same antigenic determinants as proinsulin are present in the β cells.