Molecular properties of apelin: tissue distribution and receptor binding

Biochim Biophys Acta. 2001 Apr 23;1538(2-3):162-71. doi: 10.1016/s0167-4889(00)00143-9.


We analyzed the tissue distribution of apelin mRNA in rats by a quantitative reverse transcription-polymerase chain reaction and that of immunoreactive apelin (ir-apelin) by an enzyme immunoassay (EIA) using a monoclonal antibody. The expression levels of apelin mRNA and ir-apelin seemed to be consistent among tissues: they were highly expressed in the lung and mammary gland. By the combination of gel filtration and EIA, we found that the molecular forms of apelin differ among respective tissues: apelin molecules with sizes close to apelin-36 (long forms) were major components in the lung, testis, and uterus, but both long and short (whose sizes were close to [<Glu(65)]apelin-13) forms were detected in the mammary gland. In Scatchard analyses, the radioiodinated apelin-36 analogue bound to the receptor, APJ, with high affinity. In competitive binding assays, apelin-36 and apelin-19 far more efficiently inhibited the binding of the labeled apelin-36 analogue with APJ than [<Glu(65)]apelin-13. In analyses for the dissociation of apelin from APJ, unlabeled apelin-36 replaced more rapidly the labeled apelin-36 analogue bound with APJ than [<Glu(65)]apelin-13. Our results demonstrate that the long and short forms of apelin differently interact with APJ.

Publication types

  • Comparative Study

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Apelin
  • Apelin Receptors
  • Carrier Proteins / analysis*
  • Carrier Proteins / chemical synthesis
  • Carrier Proteins / metabolism
  • Chromatography, Gel
  • Female
  • Immunoenzyme Techniques
  • Intercellular Signaling Peptides and Proteins
  • Lung / metabolism
  • Male
  • Mammary Glands, Animal / metabolism
  • Molecular Sequence Data
  • Molecular Weight
  • RNA, Messenger / analysis
  • Rats
  • Rats, Wistar
  • Receptors, Dopamine D2
  • Receptors, G-Protein-Coupled*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Testis / metabolism
  • Uterus / metabolism


  • Apelin
  • Apelin Receptors
  • Apln protein, rat
  • Aplnr protein, rat
  • Carrier Proteins
  • Intercellular Signaling Peptides and Proteins
  • RNA, Messenger
  • Receptors, Dopamine D2
  • Receptors, G-Protein-Coupled