The large expansion of the rabbit blastocyst between the 3rd and 7th day post coitum(p.c.) is due to the accumulation of fluid in the blastocoele cavity (Daniel, 1964). Na+, Cl− and HCO3 − appear to be actively transported across the trophectoderm into the blastocoele (Cross, 1973, 1974) and water moves passively secondary to NaCl accumulation (Borland, Biggers & Lechene, 1976; see also review by Borland, 1977). The trophoblast cell is physiologically polarized in that Na is transported into the blastocoele by Na/K pumps (Na+–K+ ATPase, E.C. 220.127.116.11) located on the juxtacoelic plasma membrane of the trophoblast cells (Biggers, Borland & Lechene, 1977). This functional polarity is also reflected by the anatomical polarity of the trophectoderm. Membrane junctional complexes are located at the apices of the trophoblast cell and are adjacent to fluid-filled intercellular spaces that face the blastocoele cavity (Gamow & Daniel, 1970; Enders, 1971; Hastings & Enders, 1975; Ducibella, Albertini, Anderson & Biggers, 1975). Diamond & Bossert (1967) have proposed that such closed-end channels may be the site of active solute transport that creates local standing osmotic gradients which cause water flow across epithelia.
R. M. Borland, J. D. Biggers and C. P. Lechene
L. Roblero, J. D. Biggers and C. P. Lechene
Department of Physiology and Laboratory of Human Reproduction and Reproductive Biology, Harvard Medical School, 45 Shattuck Street, Boston, Massachusetts 02115, U.S.A.
P. S. Burgoyne, R. M. Borland, J. D. Biggers and C. P. Lechene
Summary. Electron probe microanalysis was used to determine the concentrations of Na, Cl, K, Ca, Mg, S and P in samples of follicular fluid, ovarian vein serum and peripheral venous serum obtained from virgin rabbits at 2-h intervals up to 10 h after injection of hCG. Throughout this 10-h period the elemental composition of follicular fluid was essentially the same as that of blood serum. However, there was a significant drop in follicular fluid Ca relative to blood during the 10-h period which may reflect Ca involvement in the regulation of oocyte maturation. Significant differences were also found between follicles within rabbits for K and P concentrations.
R. M. Borland, J. D. Biggers, C. P. Lechene and M. L. Taymor
Summary. Relatively undisturbed samples of human oviduct fluid were obtained by aspiration into a Silastic catheter inserted through the fimbriated end of the oviduct during surgical laparotomy. The concentrations of Na, Cl, K, Ca, Mg, S and P were determined in picolitre aliquots of this fluid using X-ray spectrometry by electron probe excitation. Human tubal fluid has a unique elemental composition characterized by high concentrations of K and Cl, but low concentrations of Ca, relative to the range of normal human serum values. Na and Mg concentrations in oviduct fluid are similar to serum levels.