our observations that transfer from the periphery can result in insulin levels in the brains of small-brained but not of large-brained animals comparable to or even , on occasion , higher than plasma levels when plasma levels are falling can account for our earlier observations ( eng and yalow , 1979 , 1980 ) that in rat but not in dog or rabbit brain insulin concentrations may be comparable to plasma levels .
C0006104
brain
C0086045
concentrations