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Anion efflux from cytotrophoblast cells derived from normal term human placenta is stimulated by hyposmotic challenge and extracellular A23187 but not by membrane‐soluble cAMP
Author(s) -
Turner M. A.,
Sides M. K.,
Sibley C. P.,
Greenwood S. L.
Publication year - 1999
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1111/j.1469-445x.1999.tb00069.x
Subject(s) - efflux , cytotrophoblast , extracellular , placenta , intracellular , chemistry , ionophore , homeostasis , medicine , endocrinology , forskolin , biophysics , stimulation , biology , biochemistry , fetus , membrane , pregnancy , genetics
SUMMARY The regulation of placental anion transport influences fetal accretion and placental homeostasis. We investigated whether efflux of 125 I − or 36 Cl − from multinucleated cytotrophoblast cells derived from human term placenta is regulated by one of three stimuli: (a) the calcium ionophore A23187, (b) a ‘cocktail’ of agents designed to raise intracellular levels of cAMP, (c) a hyposmotic solution. After loading with the appropriate isotope for 2 h and thorough washing, cells were exposed to sequential aliquots of buffer applied and removed each minute. Following an equilibration period of 5 min one of the stimuli was applied at room temperature At the end of the experiment the cells were lysed to give a lysate count which was used to express the count obtained from each aliquot as percentage efflux of that possible for that minute. The cAMP ‘cocktail’ and A23187 were applied for 5 min; the hyposmotic solution was applied for 10 min. The results for 125 I − at 7 min showed that the mean efflux in the presence of hyposmotic shock was greater than control (5.7 ± 1.0% min −1 versus 2.2 ±0.1 % min −1 , respectively; mean ± S.E.M., n = 4 placentas). Similarly mean efflux at 6 min in the presence of A23187 was also significantly greater than control (6.5 ±1.9 % min −1 versus 2.6 ± 1.0 % min −1 , respectively, n = 3 placentas). The mean efflux in the presence of the cAMP cocktail was not different from control at any time point. The results were qualitatively the same if 38 Cl − was used in the place of 125 I − and when the experiment was performed with 36 Cl − in a HCO 3 − buffer gassed with CO 2 . Mean 125 I − efflux at 6 min in response to hyposmotic challenge was 33 % less ( P < 0.01) in the presence of 1 mM 4,4′‐diisothiocyanatostilbene‐2,2′‐disulphonic acid (DIDS) and 37% less ( P <0.005) in the presence of 10 μ m tamoxifen but no different if the hyposmotic solution was nominally calcium free. We conclude that there are differential effects of second messengers on anion efflux from the differentiated cytotrophoblast cells.