Properties of volume-activated taurine and iodide efflux from term human placental tissue.
The effect of cell swelling, induced by a hyposmotic challenge, upon the efflux of radiolabelled taurine and iodide from term human placental tissue explants has been studied. A hyposmotic shock markedly increased the unidirectional efflux of taurine in a manner which was fully reversible. It took approximately 6-8 min for taurine efflux to reach a maximum response following a hyposmotic challenge whereas it took about 16 min for taurine efflux to return to a basal level. This suggests that factors other than, or in addition to, membrane stretch are involved in the signal transduction process. A prolonged hyposmotic challenge appeared to inactivate volume-sensitive taurine release. Volume-activated taurine efflux was dependent upon the extent of cell swelling: the effect was greatest when the decrease in the osmolality was greater than 27 per cent. Cell swelling-induced taurine efflux was markedly inhibited by diiodosalicylate and to a lesser extent by bumetanide and quinine. A hyposmotic challenge also increased the efflux of iodide via a pathway which was sensitive to niflumic acid. This is consistent with the presence of volume-activated Cl(-)channels. Volume-activated amino acid and anion (Cl(-)) efflux may act in parallel with K(+)efflux to regulate placental cell volume following swelling.
Shennan
D B
DB
Hannah Research Institute, Ayr, KA6 5HL, Scotland, UK.
D001692:Biological Transport; D048429:Cell Size; D005260:Female; D006706:Homeostasis; D006801:Humans; D007454:Iodides / Q000378:metabolism*; D007457:Iodine Radioisotopes; D009997:Osmotic Pressure; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D013654:Taurine / Q000378:metabolism*; D014316:Tritium
D007454:Iodides; D007457:Iodine Radioisotopes; D014316:Tritium; D013654:Taurine