Placental transport of the non-metabolisable alpha-aminoisobutyric acid in guinea-pigs given a commercial chlorobiphenyl preparation or a defined, pure chlorobiphenyl.

Abstract

The placental transfer of the non-metabolisable alpha-aminoisobutyric acid was studied by means of a perfusion technique in pregnant guinea-pigs given the commercial chlorobiphenyl preparation, Clophen A50 (C-A50) or pure 2,2',4,4',5,5'-hexachlorobiphenyl (HCB), during different periods of gestation. It was shown that a total dose of 30 mg of HCB given during the latter part of gestation (day 45 to 61) decreased amino acid transport, while 30 mg of C-A50 did not. At a dose of 30 mg daily given from day 28 to day 61, again only HCB decreased the amino acid transfer. An amount of 60 mg C-A50 was required to reduce this transport. The concentration of the amino acid in blood from foetuses remaining in the uterus was significantly increased when the dams were given 60 mg of C-A50, indicating a reduced foetal uptake of the amino acid. It is suggested that the decreased placental transfer of the amino acid is dependent on physio-chemical interactions (e.g. caused by hydrophobic properties) between the chlorobiphenyls and the NaK-ATPase enzyme complex which is involved in amino acid transport.