Molecular identification of two types of interleukin-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-1 alpha in the murine adenohypophysis, but not in the neural or intermediate lobes. Specific binding of IL-1 to isolated pituitary membranes revealed a Kd of 0.9 nM with a Bmax 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 cells and establish that these receptors are similar at the molecular level to those first identified on T and B lymphocytes.