ABSTRACT
Figure3Relativehydrolysisofretinylestersbyratbrushbordermembranes.Relativeactivityispresentedasapercentageofhydrolyticactivityobservedforretinyl palmitate(16:0),comparedforhydrolysisstimulatedbyeither0.5%deoxycholate (top:retinylpalmitatehydrolysis,31.6nmol/min/mgprotein)or1.0%taurocholate (bottom:retinylpalmitatehydrolysis,8.7nmol/min/mgprotein).Chainlengthrefersto thenumberofcarbonsinthesaturatedfattyacylmoietyoftheester.(Adaptedfrom Ref.21.)
Figure4Relativehydrolysisofretinylestersbybrushbordermembranes(fromrats aftercommonductligation)andbypurebovinecarboxylesterhydrolase.Relativeactivity isthepercentageofhydrolyticactivityobservedforretinylpalmitate1.0%taurocholateby brushbordermembrane(top:1.5f.lgprotein,6.2nmolhydrolyzed/min/mgprotein)orby CEHbottom:30ng,420nmolhydrolyzed/min/mgprotein).(AdaptedfromRef.21.)
be estimated that the activity present could retinyl palmitate in 2 min to of the rat (21 ). Further
Uptakrt; After the required hydrolysis of retinyl esters, the liberated retinol (or retinol that might be in the involve a specific carrier in the brush border membrane. of retinol has been examined in the unanesthetized rat of retinol through isolated intestinal segments with intact vascular and circulation (22). Hyperbolic kinetics were observed at low concentrations with observed above 0.2-0.3 At higher levels (examined up to 2.7 linear relationship between concent·::;t1:::r and obtained, consistent with passive diffuslion. The retinol was mixed with oleic acid, mcmoo1e:n1, taurocholate. c;verted sacs revealed the satnr2bie was energy carrier-mediated passive aos:orr;:i\'t(''' '"''-''·A~""· Little effect wm; pH, taurocholate concentration, length of observed were 30-40 pmol/min length. find significant effects on retino.l. when perfusion;;; periods. Retinol uptake '""''''"'c'"'A' when was decreased, when taurocholate concentration was increased, and when octanoic acid was present.
