Mechanisms of Amino Acid Uptake in Cumulus-Enclosed Mouse Oocytes

Abstract

The nutritional role of mouse granulosa cells on antral dictyate mouse oocytes was studied by measuring the transfer of different amino acids through gap junctional channels between somatic and germ cells. When present in the incubation medium at concentrations resembling in vivo conditions, glycine, alanine, proline, serine, tyrosine, glutamic acid and lysine entered cumulus-enclosed oocytes cooperatively, while valine, leucine and phenylalanine did not. Cooperative uptake of leucine and phenylalanine was observed at higher external precursor concentrations. In vivo antral mouse oocytes apparently depend on surrounding granulosa cells for amino acid uptake, with the exception of amino aids carried by the leucine exchange transport system. Amino acid transfer between granulosa cells and oocytes could be dependent on precursor concentrations in the coupled cells.