THERE ARE TWO MAJOR HEXOSE SUGARS THAT ARE ESSENTIAL FOR GROWTH, DEVELOPMENT AND MAINTENANCE OF CELLS, TISSUES, ORGANS ANDWHOLE ORGANISMS INCLUDING THE EMBRYO/FETUS AND ITS PLACENTA WHICH ARE KNOWN COLLECTIVELY AS THE CONCEPTUS. THOSE TWO HEXOSESUGARS ARE GLUCOSE AND FRUCTOSE. THE UTERUS TRANSPORTS ABUNDANT AMOUNTS OF GLUCOSE INTO THE LUMEN OF THE PREGNANT UTERUSAND THE TROPHECTODERM/PLACENTA AND EMBRYO/FETUS USE SOME OF IT FOR PRODUCING ENERGY, BUT THAT NOT USED IS CONVERTED TOFRUCTOSE. FRUCTOSE IS INTERESTING BECAUSE ONCE IT GETS INTO THE PREGNANT UTERUS IT CANNOT BE TRANSPORTED BACK TO THE MOTHER.CONSEQUENTLY, THE SHEEP AND PIG CONCEPTUS HAS TWO HEXOSE SUGARS, GLUCOSE AND FRUCTOSE, THAT IT CAN USE TO GAIN ENERGYNECESSARY FOR IT TO GROW AND DEVELOP, FOR A FULLY DEVELOPED PLACENTA AND SURVIVE UNTIL THE TIME OF BIRTH. GLUCOSE IS KNOWN TO BEMETABOLIZED BY MANY METABOLIC PATHWAYS TO SUPPORT GROWTH AND DEVELOPMENT OF THE CONCEPTUS, BUT LITTLE IS KNOWN OF THE ROLES OFFRUCTOSE. THIS IS TRUE EVEN THOUGH THERE IS 10 TO 33 TIME MORE FRUCTOSE THAN GLUCOSE IN FETAL BLOOD, FOR EXAMPLE. WE ALSO NOW KNOW THAT CONCEPTUS TROPHECTODERM OF SHEEP AND PIGS CAN TRANSPORT BOTH GLUCOSE AND FRUCTOSE FROM MOTHER TO FETUS. IN THISSTUDY WE WILL SEEK TO UNDERSTAND THE CONTRIBUTIONS OF BOTH GLUCOSE AND FRUCTOSE AS THEY ARE METABOLIZED TO PRODUCE ENERGY,BUILDING BLOCKS FOR DNA AND RNA AND METHYL GROUPS THAT ARE INVOLVED IN MODIFYING EXPRESSION OF GENES REQUIRED FOR SURVIVAL,GROWTH AND DEVELOPMENT OF SHEEP AND PIG CONCEPTUSES. RESULTS OF OUR RESEARCH CLEARLY DEMONSTRATE THAT BOTH GLUCOSE AND FRUCTOSE CAN BE USED AS SUBSTRATES FOR THE PENTOSE CYCLE, HEXOSAMINE BIOSYNTHEIS PATHWAY, TRICARBOXYLIC ACID CYCLE TO GENERATE ATP FOR ENERGY AND LACTATE FOR FURTHER METABOLISM, AND ONE-CARBON METABOLISM PATHWAY THAT WE FIND TO USE BOTH SERINE FROM MEDIUM AND BOTH GLUCOSE AND FRUCTOSE. EACH OF THESE METABOLIC PATHWAYS ARE ESSENTIAL TO GROWTH, DEVELOPMENT AND SURVIVAL OF MAMMALIAN CONCEPTUSES.