Anion transport by human placenta: a study of chloride and sulphate efflux from isolated placental tissue fragments.

The efflux of radiolabelled sulphate and chloride from fragments prepared from normal human term placentae has been examined so that a comparison between the transport properties of whole tissue and isolated placental membranes may be made. Sulphate efflux was found via a temperature- and DIDS sensitive mechanism. External chloride and sulphate were able to trans-accelerate the egress of labelled sulphate from tissue fragments via a DIDS-inhibitable route. These results are consistent with sulphate transport being mediated via an anion-exchange process. Chloride efflux from fragments of placenta was via a system which could be trans-stimulated by external Cl-: this moiety of transport was inhibited by DIDS. Several differences between the characteristics of placental tissue anion transport and isolated membrane vesicles were noted and are discussed.