Precursors of the purine backbone augment the inhibitory action of hypoxanthine and dibutyryl cAMP on mouse oocyte maturation.
In this study we have tested the hypothesis that precursors of the purine base backbone--glutamine, glycine, aspartic acid, and formate--promote meiotic arrest when included in medium containing established meiotic inhibitors and that this occurs in glucose-dependent fashion. An initial experiment established that in medium supplemented with 4 mM hypoxanthine and containing no purine precursors, very little meiotic arrest was maintained in cumulus cell-enclosed oocytes after 17-18 hr (90% germinal vesicle breakdown; GVB). Increasing concentrations of glucose reduced the maturation percentage such that only 57% had matured at 0.55 mM. The addition of 2 mM glutamine (Gln) alone reduced the maturation percentage in the absence of glucose (70% GVB), and the further addition of glucose revealed an additive inhibitory effect between these two supplements. Dose response experiments with Gln, glycine (Gly), aspartic acid and formate showed that in medium supplemented with hypoxanthine, very little inhibitory action was observed in the absence of glucose but that upon addition of this hexose, a dramatic decrease in maturation percentage was observed in the Gln and Gly groups. Results of experiments using combinations of precursors showed that when Gln and Gly were added together, greater augmentation of meiotic arrest maintained by either hypoxanthine or dibutyryl cAMP was achieved in the presence of glucose than with either amino acid alone. The addition of purine precursors significantly increased the extent of purine nucleotide production by oocyte-cumulus cell complexes, and this was accentuated by glucose. It is concluded that the presence of purine precursors can augment the meiosis-arresting action of established meiotic inhibitors in glucose-dependent fashion, and that this is due, at least in part, to their incorporation into purine nucleotides via the de novo synthetic pathway.
Biology Department, Marquette University, Milwaukee, Wisconsin 53233, USA.
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D000818:Animals; D001224:Aspartic Acid / Q000494:pharmacology; D003994:Bucladesine / Q000737:chemistry / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005561:Formates / Q000494:pharmacology; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology; D005973:Glutamine / Q000494:pharmacology; D005998:Glycine / Q000494:pharmacology; D019271:Hypoxanthine / Q000737:chemistry / Q000494:pharmacology*; D008540:Meiosis / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008956:Models, Chemical; D009865:Oocytes / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D011685:Purine Nucleotides / Q000378:metabolism; D011687:Purines / Q000737:chemistry*; D013329:Structure-Activity Relationship
D005561:Formates; D011685:Purine Nucleotides; D011687:Purines; D005973:Glutamine; C030544:formic acid; D019271:Hypoxanthine; D001224:Aspartic Acid; D003994:Bucladesine; D005947:Glucose; D005998:Glycine