Download Amino acids in the human placental intervillous space

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BIOCHEMICAL SOCIETY TRANSACTIONS
Schatzmann, H. J. (1953) Helu. Physwl. Pharmacol. Acta 11, 3 6
354
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Stewart, G. W., Ellory, J. C. & Klein, R. A. (1980) Nahrre (London)
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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
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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,
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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
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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.
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