BIOCHEMICAL-EVIDENCE OF THE SODIUM INFLUX STIMULATING RELATED PEPTIDEIN THE BRAIN OF THE LEECH THEROMYZON TESSULATUM

This paper reports the immunocytochemical and biochemical evidence of a sodium influx stimulating related peptide (SIS-like peptide) in the brain of the leech Theromyzon tessulatum. Cells immunoreactive to both polyclonal antisera raised against the N-terminal (fragment 10-19) or the C-terminal (fragment 67-76) sequences of the purified freshwater snail Lymnaea stagnalis sodium influx stimulating peptide (SISP) was d etected in the brain of this leech. These immunocytochemical data were strengthened by biochemical results at the level of the protein and b y in vitro translated RNA. By combined techniques i.e. high performanc e gel permeation chromatography, electrophoresis followed by immunoblo t analysis with the two antisera and immunoprecipitation, we establish ed the existence in leeches of a protein of ca 11 kDa and its precurso r, a protein of ca 13 kDa related to the SISP. Moreover, results of in jections of anti-SISP (10-19) preadsorbed or not with its homologous a ntigen to Theromyzon tessulatum confirmed the SIS-like substance invol vement in osmoregulation by an anti-diuretic function.