Comparative tensile and relaxation experiments on fresh and glutaraldehyde-treated porcine aortic valve tissue

Abstract

Intracellular concentration gradients of substrate were obtained when rat-liver slices were incubated in Krebs-Ringer bicarbonate buffer with α-amino[1-14C]isobutyric acid (AIB) under conditions of aerobiosis but not anaerobically. Under aerobic conditions insulin did not affect the uptake of AIB. No concentration gradient was obtained when these slices were incubated in medium containing [1-14C]cycloleucine. No gradients were observed with various radioactive sugars including α- and β-methyl glycosidases, 3-O-methyl glucose, β-methyl thiogalactoside and potassium galactonate. Various attemps to influence the influx of α-methylglycoside by addition of possible competitive inhibitors, by the use of phlorizin, dinitrophenol and Na+-free media were without effect. It is concluded that concentration gradients involving an active transport process have been demonstrated by AIB but there was no evidence to confirm the presence of any active transport mechanism for sugars.