Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
314 BIOCHEMICAL SOCIETY TRANSACTIONS Schatzmann, H. J. (1953) Helu. Physwl. Pharmacol. Acta 11, 3 6 354 Simons, T. J. B. (1976) J . Physiof. (London) 256, 227-244 Stewart, G. W., Ellory, J. C. & Klein, R. A. (1980) Nahrre (London) 286,403-404 Wieth, J. 0. (1970) J . Physiol. (London) 207, 563-580 Amino acids in the human placental intervillous space N. McINTOSH,* C. H. RODECKt and R. HEATH* *Department of Child Health, St. George’s Hospital Medical School, Tooting. London SW17 ORE, U.K., and ?Department of Obstetrics, King’s College Hospital Medical School, Denmark Hill, London SE5 9RS. U . K . The interface between the maternal placental bed and the syncytiotrophoblastof the foetal placenta is the intervillous space which contains maternal blood. Placental hormones are released into the maternal blood of this space rather than the foetal capillaries, and maternal nutrients are extracted by the placenta for the growth and development of the foetus. Although the ultrastructure of the intervillous space has been well demonstrated (Aherne & Dunhill, 1966), even in the experimental animal it has been almost impossible to sample froin this site. Thus the knowledge of the physiology is confined to the histochemical boundaries rather than to the maternal blood within the space. It has been possible to obtain blood at foetoscopy by sampling under direct vision, which is likely to be from the intervillous space. The amino acid composition of this plasma has been compared with that of the simultaneously sampled blood from the maternal vein and the umbilical cord. Six mothers of 1 6 1 9 weeks gestation were subjected to foetoscopy and foetal blood sampling prior to termination of pregnancy for social reasons or those of known foetal abnormality. Accurate dating of pregnancy was from the last menstrual period date and was confirmed by ultrasound (Rodeck, 1980). The mothers fasted for 10-12h and the sampling was performed with them conscious but sedated. Four of the foetal samples were from the umbilical vein and two from the artery. Concurrent maternal venous samples were obtained. The 27-gauge needle was then inserted into the region of the placenta and placental bed. In these six instances, blood was obtained which was thought by the operator as likely to be from the maternal intervillous space (this represents 30% of patients where intervillous sampling was attempted). Separation of plasma and cells was immediate, with plasma stored at -20°C until analysis. Samples were deproteinized and analysed on an LKB 4400 automatic analyser. The inter-assay coefficient of variation of calibration standards was 8.6% (range 3.8-10.8%). The mean levels of the individual amino acids are shown in Fig. 1. The values of urea and ammonia are included as other potential nitrogen sources. The foetal levels are plotted as a continuous line and solid circles, maternal as broken line and open circles, and probable intervillous space samples as dotted line and open triangles. It can be seen that the intervillous-space concentrations are very similar to those of the maternal vein taken concurrently (none were significantly different), but they are very different from the foetal umbilical-cord levels (20 were significantly different). This raises the possibility as to whether the samples from the presumed intervillous space were in fact from a larger maternal vessel. Against this possibility is that the ammonia concentration in the intervillous sample is more than twice that of either the umbilical cord or maternal plasma. It is known that the foetal urea-cycle enzymes in the liver can function from 16 weeks gestation (Hagerman, 1964), but that the placenta itself does not have these and thus ammonia will be - - a ... .. .. .. . . .. .. Aminoacid.. . Gln Lys Ala Val Thr Pro Gly Ser Leu Om Tau Arg His Glu Ile Phe Eth Tyr Asn Met Cit 700 600 500 NH, 10 Fig. 1. Mean amino acid concentrations in plasmas from umbilical cord (@), maternal vein (0) and intervillous space (A) Abbreviations for less-well-knownamino acids: Om, ornithine; Tau, taurine; Eth, ethionine; Cit, citrulline. 1984 315 605th MEETING, STRATHCLYDE transferred from the placenta to the mother for clearance (Raiha, 1981). It has technically only been possible in a proportion of cases to sample the intervillous space. This is possibly not surprising, as although the estimated volume of the space in the human near term is 150ml (Aherne & Dunhill, 1966), it must be considerably smaller at this gestation (16-19 weeks). The channel size of the intervillous space varies over a wide range, rarely being 2mm diameter, but more usually being 4-20pm (Adamsons & Myers, 1975). It is concluded that this sampling technique may give more information about the physiology and endocrinology at the utero-placental interface. We thank Mrs. S. Garrett for secretarial assistance. This research was supported by a grant from the National Fund for Research into Crippling Diseases. Adamsons, K. & Myers, R. E. (1975) in The Placenta (Gruenwald, P., ed.), chapter 9, MTP Press, Lancaster Aherne, W. & Dunhill, M. S. (1966) J . Parhol. Bacteriol. 91, 123.139 Hagerman, D. D. (1964). Fed. Proc. Fed. Am. Soc. Exp. Biol. 23, 785-790 Raiha, N . R. C. (1981) in Scientific Foundations of’ Paediatrics (Davis, J. A. & Dobbing, J., eds.), chapter 8, William Heinemann Medical Books Ltd., London Rodeck, C. H. (1980) Br. J . Obstet. Gynaecol. 87, 4 4 9 4 5 6 Plasma amino acids in the mid-trimester human foetus N. MclNTOSH*, C. H. R O D E C K t and R. HEATH* *Department of Child Health, St, George’s Hospital Medical School, London SW17 ORE, U.K.. and tDepartment of Obstetrics, King’s College Hospital Medical School, Denmark Hill, London SE5 9RS. U . K . foetus is dependent. Previously acquired data on the relationship of maternal and foetal plasma amino acid levels have been from umbilical-cord specimens obtained after delivery of either the term foetus (Young 8c Prenton, 1969) or the preterm foetus (Cockburn et al., 1971). The foetal results may possibly be spurious, due to the contractions of labour, or, if the foetus is delivered by Caesarian section, the placental manipulation during delivery (Cockburn et al., The amino acids passed from the mother to the foetus are the building blocks on which the protein formation of the I 100- :: i B i i f : i Amino acid Gln : : dI nnnnn m nnn n nn rlnn n Ala Val Thr Lys Gly Pro Ser Leu Glu His Tau Eth Phe Asn lie Orn i : Er nn Met Cit Fig. 1 . Comparisonof’ amino acid concentrations in maternal cenous plasma with thost) in ,foetal umbilical wnous plasma Concentrations are shown in descending order. Results are meansks.E.M. 0, Maternal; , foetal. Abbreviations for lesser-known amino acids : Tau, taurine; Eth, ethionine; O m , ornithine; Cit, citrulline. VOl. 12