
%0 Journal Article
%A Alvaro, Ruben E. 
%A Robertson, May 
%A Al-Saedi, Saad 
%A Lemke, Robert P. 
%A Cates, Don B. 
%A Rigatto, Henrique 
%T Preliminary characterization of a placental factor inhibiting breathing in fetal sheep
%J Reproduction, Fertility and Development
%D 1998/03/23
%V 9
%N 6
%P 641-650
%K control of breathing, umbilical circulation, placental dissection, spontaneous fetal breathing, purication and characterization.
%R https://doi.org/10.1071/R97031
%U https://www.publish.csiro.au/paper/R97031 
%X Previous studies have revealed a placental extract that inhibits breathing in fetal sheep. In the present study of 29 chronically instrumented sheep at 132&#177;1 days of gestation, infusion of the 1-10 kDa extract inhibited breathing in 76% of the experiments whereas Krebs&#8217; solution inhibited it in 24%. It retained this activity after 6 months of freezing, after lyophilization, and upon lowering the pH during purication from 8&#183;0 to 4&#183;0, but it inhibited breathing in only 35% when the pH was lowered to 2&#183;0. A signicant 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&#183;0 or 8&#183; 0, but it was at pH 9&#183; 0 and it eluted with increasing NaCl concentrations. On a polyacrylamide gel the activity was eluted at a Kav of 0&#183; 66 (82% inhibition), corresponding to between 2&#183;5 and 4&#183;5 kDa. These ndings suggest that a peptide produced by the placenta, with a molecular mass between 2&#183; 5 and 4&#183;5 kDa, inhibits fetal breathing. 
