Molecular Identification of Two Types of lnterleukin‐1 Receptors in the Murine Pituitary Gland

The present study was carried out to characterize interleukin‐1 (IL‐1) receptors on murine pituitary cells. Receptor autoradiography confirmed the existence of binding sites for IL‐1α in the murine adenphypophysis, but not in the neural or intermediate lobes. Specific binding of IL‐1 to isolated pituitary membranes revealed a K_d of 0.9 nM with a B_max of 37 fmol/mg protein. To examine the possibility that the adenohypophysis synthesizes a receptor for IL‐1, immunocytochemistry experiments with a specific monoclonal antibody against the type I receptor revealed the existence of this protein in only the adenohypophysis. Identity of the type I IL‐1 receptor was similar to that found on T cells as determined by: 1) amplification of the predicted 619 bp fragment spanning the cytoplasmic, transmembrane and extracellular domains from RNA of pituitary and T cell origin, as well as clonal AtT‐20 pituitary cells, and 2) restriction fragment analysis and sequencing of the amplified cDNAs. The pituitary gland and AtT‐20 cells also expressed transcripts for the newly identified type II receptor for IL‐1 as assessed by amplification of a specific 325 bp fragment, restriction fragment analysis and nucleotide sequencing, and these transcripts were similar to those found on B lymphocytes. These data identify two different forms of the IL‐1 receptor in both normal and transformed pituitary calls and establish that these receptors are similar at the molecular level to those first identified on T and B lymphocytes.