The Effect of Insulin Deficiency on the Glutathione-Insulin Transhydrogenase Activity of Rat Liver

Abstract

first begin to eat solid food. It is possible that the high circulating glycosidase activities in the sera of pregnant and young rabbits are associated with the metabolism of oligosaccharides derived from maternal milk. Each tissue had its own specific pattern of development for N-acetylglucosaminidase during the first 35 days after birth. In liver N-acetylglucosaminidase activity was higher in newborn animals than in adults (P t0.005) and continued to rise until day 14 after birth; thereafter activities fell and adult values were seen in 28-day-old animals. In spleen and kidney (Figs. 2c and 2d) N-acetylglucosaminidase activity in newborn animals was lower than in adults (P = 0.0005). In kidney the pattern of development was biphasic, whereas in spleen N-acetylglucosaminidase activity rose steadily until adult activities were attained by 35 days. Electrophoresis showed that in kidney and liver all the adult forms were present in newborn animals. In the spleens of these rabbits no forms of the enzyme were detectable, but as enzyme activity increased with age the various forms appeared. In neonatal heart and brain N-acetylglucosaminidase activity was similar to that in the adult tissues (Figs. 2e and 2f). Brain enzyme activity increased until 14 days (0.005 >P>0.0025), after which time the mean activity did not vary statistically. Examination of cerebral tissue by electrophoresis showed that these increases were accompanied by the appearance of an electrophoretic form. Liver and hearts of neonatal rabbits had higher acid a-mannosidase activity than did the same tissues in mature animals (0.01 >P>0.005; 0.005 >P>0.0025 respectively). In spleen both acid and neutral forms had lower activities thanin adults (0.01 >P>0.005), although in no tissue were the changes in activity as marked as for N-acetylglucosaminidase. For young rabbits both enzyme forms in kidney and heart had similar activities, in contrast with the adult animals, where the neutral form had higher activity than the acid (P = 0.01 and 0.05 >P>0.025 respectively). These results show that in early life the changes in rabbit tissue N-acetylglucosaminidase activity are different from a-mannosidase and it may be that each glycosidase has a distinct pattern of development. By 5 weeks after birth, the earliest stage at which young laboratory rabbits are capable of existence independent from their mothers, adult activities and electrophoretic forms of the enzymes were established in all tissues studied except brain. In both spleen and brain changes in N-acetylglucosaminidase activity were accompanied by alterations in electrophoretic patterns. Perhaps these changes are associated with developmental processes in early life; in brain this may be myelination and in spleen it may be the change from a haemopoietic to haemolytic function. Carroll, M., Dance, N., Masson, P. K., Robinson, D. &Winchester, B. G. (1972) Biochem. Bio