Water permeability of an ovarian antral follicle is predominantly transcellular and mediated by aquaporins.
Ovarian folliculogenesis is characterized, in part, by the formation and expansion of the fluid-filled antrum. Development of this cavity requires water influx, which may occur by transcellular or pericellular transport mechanisms. To assess the contribution of these mechanisms to the water permeability of an antral follicle, the rate of (3)H(2)O and (14)C-inulin (a complex sugar restricted to the extracellular compartment) uptake into isolated follicles was determined. The rate of H(2)O movement was 3.5-fold greater than that of inulin, suggesting that water enters a follicle primarily by transcellular pathways. Preincubation of the follicles with 50 microM HgCl(2) [a nonspecific aquaporin (Aqp) inhibitor] decreased H(2)O movement to levels seen with inulin, indicating that transcellular water movement is mediated through Aqp. To demonstrate the functional presence of Aqp in granulosa cells, we show that swelling in response to a hypotonic insult is attenuated by preincubation with 50 microM HgCl(2). Flow cytometry demonstrated the presence of Aqps-7, -8, and -9, thus identifying candidate Aqp potentially mediating water movement into antral follicles. These results suggest that water permeability of antral follicles occurs primarily through transcellular mechanisms, which may be mediated by Aqps -7, -8, and/or -9 in granulosa cells.
McConnell
Nisha A
NA
Department of Biology, University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, NC 28223, USA.
Yunus
Raheela S
RS
Gross
Stephen A
SA
Bost
Kenneth L
KL
Clemens
Mark G
MG
Hughes
Francis M
FM
D000818:Animals; D020346:Aquaporins / Q000032:analysis / Q000502:physiology*; D001834:Body Water / Q000378:metabolism*; D005260:Female; D006107:Granulosa Cells / Q000737:chemistry; D007473:Ion Channels / Q000032:analysis / Q000502:physiology*; D008627:Mercuric Chloride / Q000494:pharmacology; D006080:Ovarian Follicle / Q000378:metabolism*; D010539:Permeability; D051381:Rats; D017207:Rats, Sprague-Dawley
C491926:Aqp7 protein, rat; C491637:Aqp9 protein, rat; D020346:Aquaporins; D007473:Ion Channels; C108330:aquaporin 8; D008627:Mercuric Chloride