Galactose metabolism in human ovarian tissue

Galactose metabolism was studied in human ovarian tissue obtained from 14 women controls between 21 and 72 y of age, and one 21-y-old galactosemic patient with hypergonadotrophic hypogonadism. Tissue slices were incubated with 1-14C-galactose, and labeled intermediates were analyzed by anion-exchange column chromatography. Activities of enzymes related to the galactose pathway: galactokinase, transferase, epimerase, uridine diphosphoglucose (UDPGlc) and uridine diphosphogalactose pyrophosphorylases, and UDPGlc and uridine diphosphogalactose pyrophosphatases were measured in ovarian homogenates using radioisotopic, spectrophotometric, and fluorometric techniques. Incorporation of carbon label from 1-14C-galactose into various galactose and glycolytic intermediates, as well as carbon dioxide and TCA-insoluble materials was demonstrated in samples from non-galactosemic controls. In tissue from the galactosemic individual, no labeled carbon dioxide was produced and very little incorporation into TCA-insoluble material was found. Labeled galactose-1-phosphate was elevated. In normal ovarian tissue, specific activities of galactokinase, transferase, epimerase, and UDPGlc pyrophosphorylase are much higher than those found in the red cells and in testes. UDPGlc pyrophosphorylase activity is about 50 times that of transferase, suggesting that uridine nucleotide sugars have an important role in the normal development and function of the ovary. It is hypothesized that premature ovarian failure, often observed in patients with galactosemia, is due to interference with nucleotide sugar metabolism and the synthesis of galactose containing glycoproteins and glycolipids consequent to the enzymatic defect in the major pathway of galactose metabolism.