INCREASED GLUTAMINE-METABOLISM IN BOVINE CUMULUS CELL-ENCLOSED AND DENUDED OOCYTES AFTER INVITRO MATURATION WITH LUTEINIZING-HORMONE

The effects of LH on tricarboxylic acid (TCA) cycle activity within denuded and cumulus cell-enclosed bovine oocytes were investigated by measuring the metabolism of L-[C-14(U)]glutamine and [2-C-14]pyruvate to (CO2)-C-14 after in vitro maturation (IVM) with LH in serum-free, defined culture conditions. Initially, intact cumulus cell-enclosed oocytes or oocytectomized cumulus cell complexes were incubated for 24 h for IVM in control medium alone or supplemented with LH (10 mug/ml) before assessment of glutamine metabolism. Glutamine oxidation was increased (p < 0.01) only after IVM of intact cumulus cell-enclosed oocytes with LH when compared to either intact untreated controls, untreated oocytectomized controls, or oocytectomized cumulus cell complexes after LH treatment (0.23 +/- 0.02 vs. 0.13 +/- 0.01, 0.12 +/- 0.0 1, and 0.12 =/- 0.01 nmol (CO2)-C-14/mug protein/3 h, respectively). Glutamine metabolism was greater (p < 0.001) in denuded oocytes from cumulus cell complexes that were exposed to LH during IVM versus nontreated controls (6.4 +/- 0.3 vs. 5.1 +/- 0.2 pmol (CO2)-C-14/oocyte/3 h, respectively). Glutamine metabolism was increased (p < 0.05) in cumulus cell-enclosed oocytes after LH exposure during IVM but was unchanged after exposure to either FSH or thyroid-stimulating hormone when compared to control treatments (0.23 +/- 0.01, 0.20 +/- 0.02, 0.19 +/-0.01 vs. 0.16 +/- 0.02 nmol (CO2)-C-14/mug protein/3 h, respectively). Pyruvate metabolism was not different between LH and control treatments. Evidence demonstrated that LH acts via the cumulus cells to increase glutamine metabolism within intact cumulus cell-enclosed oocytes and in mature oocytes denuded after LH exposure. It is likely that this represents a means by which LH enhances oocyte quality during the maturation process.