ATRIAL NATRIURETIC FACTOR-LIKE PEPTIDE AND ITS PROHORMONE WITHIN SINGLE CELL ORGANISMS

The present investigation was designed to determine if the atrial natr iuretic peptide hormonal system is present within single cell organism s. Paramecium multimicronucleatum were examined with 3 sensitive and s pecific radioimmunoassays which recognize the N-terminus [amino acids 1-98; proANF(1-98)], the midportion of the N-terminus [amino acids 31- 67; proANF(31-67)] and C-terminus (amino acids 99-126; ANF) of the 126 amino acid atrial natriuretic factor (ANF) prohormone. ProANF(1-98), proANF(31-67), and ANF-like peptides were all present within these uni cellular organisms at concentrations of 460 +/- 19 pg/ml, 420 +/- 15 p g/ml, and 14.5 +/- 2 pg/ml, respectively. These concentrations are sim ilar to their respective concentrations in the plasma of the rat (Ratt us norvegicus). These results suggest that even single cell organisms contain the atrial natriuretic peptide-like hormonal system.