Journal
BIOLOGY OF REPRODUCTION
Volume 81, Issue 6, Pages 1041-1054Publisher
SOC STUDY REPRODUCTION
DOI: 10.1095/biolreprod.109.079046
Keywords
amino acid transport; cumulus cells; granulosa cells; meiosis; oocyte development
Categories
Funding
- Program on Oocyte Health
- Canadian Institutes of Health Research (CIHR)
- Institute of Human Development, Child and Youth Health (IHDCYH) [HGG62293]
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Amino acids are transported into cells by a number of different transport systems, each with their own specific range of substrates. The amino acid transport systems active in preimplantation embryos and the amino acids required by embryos for optimal development have been extensively investigated. Much less is known about amino acid transport systems active in growing and meiotically maturing oocytes or about developmental changes in their activity. As a first step in determining the array of amino acid transporters active in oocytes, the transport characteristics of nine amino acids were measured in small, medium, and large growing oocytes; in fully grown germinal vesicle (GV)-stage oocytes; in metaphase I oocytes; and in metaphase II eggs. Whether each of 11 classically defined amino acid transport systems was likely active in oocytes at each stage was determined using assays based on measuring the transport of radiolabeled amino acids into oocytes and the effect of a limited set of potential competitive inhibitors. Six amino acid transport systems were found to be active during oocyte growth or maturation. L, b(0,+), and ASC/asc were active throughout oocyte growth and maturation, increasing during growth. In contrast, GLY, beta, and x(c)(-) had little or no activity during growth but became activated during meiotic maturation. Surprisingly, the presence of follicular cells surrounding medium growing oocytes or cumulus cells surrounding GV oocytes did not confer amino acid transport by additional transport systems not present in the oocyte. In some cases, however, follicular cells coupled to the oocyte enhanced uptake of amino acids by the same systems present in the oocyte.
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