title: Preliminary characterization of a placental factor inhibiting breathing in fetal sheep.
abstract: Previous studies have revealed a placental extract that inhibits breathing in fetal sheep. In the present study of 29 chronically instrumented sheep at 132+/-1 days of gestation, infusion of the 1-10 kDa extract inhibited breathing in 76% of the experiments whereas Krebs' solution inhibited it in 24%. It retained this activity after 6 months of freezing, after lyophilization, and upon lowering the pH during purification from 8.0 to 4.0, but it inhibited breathing in only 35% when the pH was lowered to 2.0. A significant dose-dependent effect was observed from a 16-fold dilution to a 4-fold concentration. Treatment of the extract with proteinase K or boiling reduced the activity to 30% or 26% inhibition, respectively. The activity was not adsorbed to an ion-exchange column at pH 7.0 or 8.0, but it was at pH 9.0 and it eluted with increasing NaCl concentrations. On a polyacrylamide gel the activity was eluted at a K(av) of 0.66 (82% inhibition), corresponding to between 2.5 and 4.5 kDa. These findings suggest that a peptide produced by the placenta, with a molecular mass between 2.5 and 4.5 kDa, inhibits fetal breathing.
authors.affiliation: Department of Pediatrics, Physiology and Reproductive Medicine, University of Manitoba-Winnipeg, Canada. ralvaro@cc.umanitoba.ca
authors.forename: R E
authors.initials: RE
authors.lastname: Alvaro
authors.forename: M
authors.initials: M
authors.lastname: Robertson
authors.forename: S
authors.initials: S
authors.lastname: Al-Saedi
authors.forename: R P
authors.initials: RP
authors.lastname: Lemke
authors.forename: D B
authors.initials: DB
authors.lastname: Cates
authors.forename: H
authors.initials: H
authors.lastname: Rigatto
mesh_terms: D000818:Animals; D019286:Endopeptidase K / Q000494:pharmacology; D005260:Female; D005324:Fetal Movement / Q000187:drug effects; D005333:Fetus / Q000502:physiology*; D005612:Freeze Drying; D005865:Gestational Age; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D010920:Placenta / Q000737:chemistry*; D011247:Pregnancy; D012119:Respiration / Q000187:drug effects*; D012756:Sheep; D014020:Tissue Extracts / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D010455:Peptides; D014020:Tissue Extracts; D019286:Endopeptidase K