Expression of α,βA and βB subunits of inhibin or activin and follistatin in rat pancreatic islets

We first detected the mRNA expression of follistatin and three subunits of inhibin/activin in rat pancreatic islets by reverse transcription‐polymerase chain reaction (RT‐PCR). Immunohistochemistry using anti‐follistatin serum (against residues 123–134) revealed that follistatin was localized only in insulin‐producing B cells. Although the βA subunit was detectable in the islets, the immunostainable cell types were completely different with two βA antisera, i.e. anti‐βA (1–1O)‐Tyr stained B cells, while anti‐βA (87–99) stained glucagon‐producing A cells. This inconsistent immunoreactivity was probably related to follistatin binding to β subunits of inhibin/activin. This study indicates that follistatin and inhibin/activin in the islet serve as paracrine or autocrine modulators in the endocrine pancreas.