Perinatal development of inositol synthesis and catabolism in rabbit kidney

Inositol influences growth and perinatal development. To investigate the causes of the decrease in serum inositol levels during perinatal development, the rate-limiting enzyme activities in the catabolism and synthesis of inositol, inositol oxygenase and glucose-6-phosphate:L-inositol-1-phosphate cyclase (cyclase) were measured. The specific activity of inositol oxygenase (uniquely present in the kidney) increased 18-fold between the 25th fetal and the 17th neonatal days, and, at the same time, the specific activity of cyclase decreased by 50%. Between cortex and medulla, there were striking differences in the distribution of inositol oxygenase, when compared to the distribution of both cyclase and free inositol. Inositol supplementation during pregnancy increased serum inositol both in the doe and the fetuses, and tended to increase the inositol concentration in organs with relatively low cyclase activity and low free inositol (liver, lung). An acute oral inositol load and/or glucocorticoid intramuscularly is administered to the pregnant doe did not alter either maternal or fetal inositol oxygenase activities. It is proposed that the tissue contents of inositol are in part regulated by the rate of the endogenous synthesis. The development of inositol oxygenase activity may influence serum inositol concentrations during the perinatal period, in addition to the diet.