Reactivating tammar wallaby blastocysts oxidize fatty acids and amino acids

Abstract

The tammar wallaby, Macropus eugenii, has a ruminant-like digestive system which may make a significant concentration of amino acids and fatty acids available to the blastocyst via uterine fluids. Fluorescent and radioisotope analyses were performed to determine the rate of glutamine and palmitate use by blastocysts recovered on day 0, 3, 4, 5 and 10 after reactivation induced by removal of pouch young (RPY). Between day 0 and 4 glutamine uptake increased from 15.6 ± 6.6 to 36.1 ± 2.7 pmol per embryo h-1 (P < 0.01) and ammonium production increased from 8.2 ± 4.3 to 26.6 ± 3.0 pmol per embryo h-1 (P < 0.01). Glutamine oxidation did not increase until day 10 after RPY (P < 0.01), but the percentage of glutamine oxidized increased from 4.5 ± 3.1% during diapause to 31.2 ± 12.6% (P < 0.01) by day 5 after RPY and increased further to 51.0 ± 15.8% (P < 0.01) by day 10 after RPY. Palmitate oxidation also increased from 0.3 ± 0.1 by day 0 blastocysts to 3.8 ± 1.7 pmol per embryo h-1 (P < 0.01) by day 4 blastocysts. This increase provides a greater potential for ATP production, possibly to supply increased demand due to the coincident resumption of mitoses. The ATP:ADP ratio within blastocysts had reduced by the time of the first measurement at day 3 (0.5 ± 0.2 pmol per embryo h-1; P < 0.01) compared with day 0 blastocysts (1.4 ± 0.3 pmol per embryo h-1). It is likely that metabolism of amino acids and fatty acids contributes to the energy supply during reactivation of tammar wallaby blastocysts after embryonic diapause.