Amino Acid Transport in Follicles Isolated from the Rabbit Ovary THOMAS M. MILLS AND ERIC I. FEIT Department of Endocrinology, Medical College of Georgia, Augusta, Georgia 30902 suppressed the LH effect on AIB transport, inhibitors of protein synthesis increased the rate of AIB movement into follicles. The in vitro transport of AIB was also studied in follicles isolated 2 h after mating and in ovulated follicles which were obtained 12 h after coitus. AIB transport rate showed a rise following mating but fell to less than precoital rates in ovulated (12 h) follicles. Transport in both 2 and 12 h follicles proved unresponsive to LH stimulation. Taken together, these studies suggest that AIB transport in isolated ovarian follicles is a LHsensitive, energy-dependent process. Although AIB transport changes in a pattern qualitatively similar to that previously reported for postcoital protein synthesis, LH stimulation of the two processes may be via different mechanisms. (Endocrinology 99: 1597, 1976)
ABSTRACT. The model amino acid a-aminoisobutyric acid (AIB) has been used to investigate amino acid transport in follicles isolated from rabbit ovaries. LH markedly increased AIB transport, while incubation with FSH, cAMP or dbcAMP failed to increase the process. Several kinds of inhibitors have been utilized to characterize follicular AIB transport as an energy dependent process and apparently independent of follicular steroidogenesis. The rates of AIB efflux from preloaded follicles were measured in the presence and absence of LH; the rate measurements suggest that only the rate of entry of AIB into follicular cells is stimulated by the gonadotropin. Further experiments used inhibitors of RNA and protein synthesis to examine the relationship between AIB transport and the synthesis of macromolecules. Whereas blocking RNA synthesis
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ECENT studies from this laboratory have demonstrated an in vitro stimulating action of gonadotropins and cAMP on the incorporation of a radioactive amino acid into protein by rabbit ovarian follicles (1). A preovulatory wave of protein synthesis was also observed in the interval between mating and the coitally-induced ovulation. It was not apparent from these studies, however, whether the gonadotropins stimulated the protein synthetic process directly or indirectly by way of increasing the transport of substrate amino acids into follicular cells. The aim of the present study was to establish the presence of an active amino acid transport system in ovarian follicles, to investigate the control of this process, and, in doing so, examine the relationships between amino acid transport and the synthesis of protein. Materials and Methods Chemicals All solvents were reagent grade and most were redistilled prior to use. [U-1
Amino acid transport in follicles isolated from the rabbit ovary.
Amino Acid Transport in Follicles Isolated from the Rabbit Ovary THOMAS M. MILLS AND ERIC I. FEIT Department of Endocrinology, Medical College of Geor...