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The total glucose metabolism of 48-h spherical trophoblastic vesicles, Day-60 trophoblastic vesicles sections and Day-14 porcine blastocyst sections was measured by the method of O'Fallon and Wright (1). Trophoblastic vesicles were formed by enzyme dispersal in Day-14 porcine blastocysts. Glucose was based on DNA content of the tissue measured by diamino benzoic acid reaction with DNA (2). Slope of the lines (PMoles glucose utilized/4 h x DNA content) was different between Day-14 blastocyst sections and 48 h trophoblastic vesicles (P /= 0.05). Slopes of the lines were identical between 48-h trophoblastic vesicles and Day-60 trophoblastic vesicles sections (P >/= 0.87). Average glucose utilization on a per ng DNA basis was calculated. Day-14 blastocyst sections utilized 0.67 Pmoles glucose/4 h per ng DNA, Day-60 trophoblastic vesicles sections; 0.57; and 48-h sperical trophoblastic vesicles used 0.29. It is hypothesized that the change in glucose utilization between the Day-14 porcine blastocyst and enzymatically formed trophoblastic vesicles may be due to a decrease in metabolism as a consequence of in vitro culture. Further, it is theorized that Day-60 trophoblastic vesicles sections used higher quantities of glucose than 48-h sperical trophoblastic vesicles on a per ng DNA basis due to the increased availability of glucose to the cells of the inner layers, caused by the sectioning of the tissue. The results of this study identify changes in glucose metabolism of enzymatically formed porcine trophoblastic vesicles during culture. It is proposed that enzymatically-formed trophoblastic vesicles be used as a model system for the study of embyro metabolism.

Pig embryos were collected, 2-7 days after oestrus, in modified BMOC-2 containing glucose as the only energy source. Embryos were incubated individually in medium containing [5-(3)H]-, [1-(14)C]- or [6-(14)C]glucose. Total glucose metabolism, as measured by [5-(3)H]glucose use, increased steadily from the 1-cell to the 8-cell stage. Total glucose use increased (P less than 0.05) at the compacted morula stage and was highest (P less than 0.05) at the blastocyst stage. Production of 14CO2 from embryos metabolizing [1-(14)C]glucose increased steadily from the unfertilized ovum to the 8-cell stage. Metabolism of [1-(14)C]glucose increased at the compacted morula stage (P less than 0.05) and continued to increase (P less than 0.05) to the blastocyst stage. Metabolism of [6-(14)C]glucose increased steadily from the unfertilized ovum to the compacted morula stage. Metabolism of [6-(14)C]glucose was highest (P less than 0.05) for the blastocyst stage. Percentage pentose phosphate pathway activity of total glucose metabolism before the 4-cell stage was higher (greater than 5%) than that of 8-cell to blastocyst stage embryos (approximately 1%). When embryo metabolism was determined on a per cell basis for each isotope, the compacted morulae stage (16 cells) had a higher total glucose metabolism than all other embryo stages (P less than 0.05), while early blastocyst (32 cells) and blastocyst (64 cells) stage embryos metabolized more [5-(3)H]glucose than all stages except compacted morulae (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)