title: Amino acid transport system L activity in developing mouse ovarian follicles.
abstract: BACKGROUND
  Little is known about metabolic processes in the developing ovarian follicle. Using mouse ovarian follicles, we investigated uptake of L-leucine by follicles at varying stages of maturity in the presence of insulin-like growth factor (IGF)-1. METHODS Mouse ovarian follicles were cultured in vitro for 5 days in increasing concentrations of IGF-1, and follicle diameter and atresia measured as endpoints for growth. Uptake of (3)H-leucine was measured in follicles at different stages of development. In optimal IGF-1-mediated growth conditions, competitive inhibition of (3)H-leucine uptake by 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH), a non-metabolizable substrate analogue of L-leucine, was performed to demonstrate specificity of influx, via system L transporters. To test whether uptake rates were dependent on intracellular amino acid availability, follicles from in vitro cultures were pre-treated with L-phenylalanine prior to (3)H-leucine uptake.
  
  
  RESULTS
  Follicle development (P< 0.001) and survival (P< 0.001) increased with IGF-1 treatment. As pre-antral follicles progressed to late antral stage, we observed an increase in L-leucine uptake, which was reduced in pre-ovulatory follicles. BCH decreased L-leucine uptake rates in early antral (P< 0.05), antral (P< 0.001) and pre-ovulatory follicles (P< 0.01). L-leucine influx increased in follicles preloaded with phenylalanine (trans-stimulation). In follicles lacking free intracellular amino acids (zero-trans suppression), uptake rate was reduced (P< 0.05).
  
  
  CONCLUSIONS
  These results demonstrate, for the first time, evidence of specific system L amino acid transport in intact, mouse ovarian follicles and profile L-leucine uptake during folliculogenesis. A better understanding of ovarian follicle metabolic pathways is necessary for improved in vitro maturation as well as determining the impact of altered metabolism on fertility.
authors.affiliation: Cancer Drug Discovery, Prince Henry's Institute, Monash Medical Centre, Clayton, Melbourne 3168,  Australia.
authors.forename: Ashwini L
authors.initials: AL
authors.lastname: Chand
authors.forename: Michael
authors.initials: M
authors.lastname: Legge
mesh_terms: D027062:Amino Acid Transport System L / Q000378:metabolism*; D000598:Amino Acids, Cyclic / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D003338:Corpus Luteum / Q000378:metabolism; D005260:Female; D005298:Fertility; D018507:Gene Expression Regulation, Developmental; D006107:Granulosa Cells / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007930:Leucine / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D006080:Ovarian Follicle / Q000196:embryology* / Q000378:metabolism
chemical_list: D027062:Amino Acid Transport System L; D000598:Amino Acids, Cyclic; C006504:2-aminobicyclo(2,2,1)heptane-2-carboxylic acid; D007334:Insulin-Like Growth Factor I; D007930:Leucine