Transport of amino acids and nucleosides in metaphase-arrested unfertilized oocytes of Xenopus laevis.

Metaphase-arrested, unfertilized shed oocytes of Xenopus laevis obtained after hormonal stimulation of the female are able to take up nucleosides (U, T) and amino acids (Ala, Gly, Glu, Gln, Tyr). For alanine, tyrosine, and glutamic acid the transport is uphill. The transport of the amino acids studied is activated by Na+, whereas the uptake of the nucleosides is independent of the Na+ concentration. Ouabain does not inhibit the uptake of amino acids significantly. The uptake of alanine and thymidine is not measurably affected by the presence of the jelly coat.