MOLECULAR-IDENTIFICATION OF 2 TYPES OF INTERLEUKIN-1 RECEPTORS IN THEMURINE PITUITARY-GLAND

The present study was carried out to characterize interleukin-1 (IL-1) receptors on murine pituitary cells. Receptor autoradiography confirm ed the existence of binding sites for IL-1alpha in the murine adenohyp ophysis, 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 wit h a B(max) of 37 fmol/mg protein. To examine the possibility that the adenohypophysis synthesizes a receptor for IL-1, immunocytochemistry e xperiments with a specific monoclonal antibody against the type I rece ptor revealed the existence of this protein in only the adenohypophysi s. 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 frag ment spanning the cytoplasmic, transmembrane and extracellular domains from RNA of pituitary and T cell origin, as well as clonal AtT-20 pit uitary cells, and 2) restriction fragment analysis and sequencing of t he amplified cDNAs. The pituitary gland and AtT-20 cells also expresse d transcripts for the newly identified type II receptor for IL-1 as as sessed by amplification of a specific 325 bp fragment, restriction fra gment analysis and nucleotide sequencing, and these transcripts were s imilar to those found on B lymphocytes. These data identify two differ ent forms of the IL-1 receptor in both normal and transformed pituitar y cells and establish that these receptors are similar at the molecula r level to those first identified on T and B lymphocytes.