Ob-Ra, b, and e are the major splice forms of the leptin receptor. This study was performed to map the tissue distribution and to quantify the 3 receptor isoforms by heterologous competitive Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) and RNase Protection Assay (RNase PA). The mRNA of the truncated, membrane bound isoform Ob-Ra was found to be represented ubiquitously. Messenger RNA for the putative functional isoform Ob-Rb could be detected in brain, hypothalamus and in some peripheral tissues (e.g. heart, lung, lymph nodes). The highest ratio between Ob-Rb and Ob-Ra mRNA was found in the hypothalamus, where leptin probably exerts its satiety action. The fact that Ob-Rb mRNA was found in peripheral tissues could indicate possible additional functions of leptin. Transcripts for the shortest splice variant, Ob-Re, which is expected to encode a soluble form of the receptor, were detected in relatively high amounts in many tissues. The levels were comparable to those of leptin mRNA in fat tissue. It is conceivable, therefore, that Ob-Re might be secreted in sufficient amounts to act as a buffering system for freely circulating leptin. (C) 1997 Academic Press.
