A new born begins vomiting after feeding, becomes severely jaundiced, and has liver disease. Treatment for possible sepsis is initiated, and the urine is found to have reducing substances. A blood screen for galactosemia is positive, and lactose-containing substances are removed from the diet. Lactose is toxic in this case because of which of the following?
|A||Excess glucose accumulates in the blood|
|B||Galactose is converted to the toxic substance galactitol (dulcitol)|
|C||Galactose competes for glucose during hepatic glycogen synthesis|
|D||Galactose is itself toxic in even small amounts|
a. Lactose in breast milk and infant formula is converted by intestinal lactase to glucose and galactose that are efficiently absorbed. In galactosemia, deficiency of galactose-i-phosphate uridyl transferase prevents the conversion of galactose into glucose-6- phosphate by the liver or erythrocytes.
b. Most other organs do not metabolize galactose. The severe symptoms of galactosemia are caused by the reduction of galactose to galactitol (dulcitol) in the presence of the enzyme aldose reductase.
c. High levels of galactitol cause cataracts, the accumulation of galactose-1-phosphate contributes to liver disease, and the accumulation of galactose metabolites in urine can be measured as reducing substances by the Clinitest method.