Observations on the mono-amine oxidase activity of placenta and uterus

The original object of the investigation was to find whether the placental barrier was permeable to adrenaline and to noradrenaline. It soon became apparent that whereas the placental vessels were very sensitive to these hormones, the foetus itself was relatively insensitive. These findings will now be described. METHODSThe observations were made on rabbits, 28-31 days pregnant, and guinea-pigs, 40-63 days pregnant. Light anaesthesia was maintained with urethane 1-5 g/kg body weight, injected intravenously. The guinea-pigs were lightly anaesthetized with ether while a vein was exposed for the injection. A maternal jugular vein was cannulated with fine polythene tubing for the infusion or injection of drugs. The maternal arterial blood pressure was recorded with a capacitance manometer from a carotid artery which was also cannulated with fine polythene tubing. The abdominal wall was opened by a mid-line incision under saline at 380 C. The uterus was cut longitudinally from rump to crown of a single foetus and that foetus was then delivered into the saline and supported throughout the experiment on a gauze sling. The foetal arterial blood pressure was recorded with a capacitance manometer from one carotid artery which was cannulated with a no. 19 record needle. Intrafoetal injections were made into the jugular vein or, in the guinea-pig, into the vitelline vein, towards the foetus. RESULTSL-Adrenaline, L-noradrenaline and oxytocin in the maternal circulation A continuous infusion of adrenaline, at the rate of 06 ,ug/kg/min, increased the maternal blood pressure by 10-25 mm Hg (with or without accelerating the heart rate) and caused vigorous contractions of the uterine muscle. The placenta became blue, the foetal heart rate fell from an average value of 300 per min to 150-170 per min, and the foetal blood pressure decreased from

Section: Discussionmentioning

confidence: 99%

The action of adrenaline and noradrenaline on the placental and foetal circulations in the rabbit and guinea‐pig

Dornhorst¹,

Young²

1952

“…Measurements of 02 consumption of tissue slices or homogenates from the placentas of man, rabbit, rat, mouse and guinea-pig were made under varying conditions by Murphy & Hawkins (1925), Fujita (1928), Blair Bell, Brook & Jowett (1928, Adler (1930), Loeser (1932), Wang & Hellman (1943), Thompson & Tickner (1949), Hellman, Harris & Andrews (1950, Villee (1953), Kyank (1954), Domany, Csaba & Szekely (1956), Nyberg & Westin (1957), McKay (1958), and Friedman & Sachtleben (1960. The 02 consumption ranged from 1-3 to 75 5,l./mg dry wt.…”

Section: Discussionmentioning

confidence: 99%

The oxygen consumption of the placenta and foetal membranes in the sheep

Campbell¹,

Dawes²,

Fishman³

et al. 1966

SUMMARY1. In anaesthetized sheep near term the 02 uptake of the foetus from the placenta was reduced to zero either by replacing the foetus with a mechanical pump, or by ventilation of the foetus after delivery or in utero. When umbilical arterial and venous Po. were made equal, they were much less than maternal arterial Po2.2. This difference in Po2 was attributed to 02 consumption both within the placental cotyledons and the extra-cotyledonary foetal membranes. 3. The foetal membranes and cord in the sheep are supplied by branches of umbilical blood vessels and constitute an oxygen-consuming by-pass on the foetal side of the placenta.4. The 02 consumption of individual placental cotyledons was measured in vivo.5. The combined 02 consumption of the whole placenta and foetal membranes in vivo was a considerable fraction of foetal 02 consumption.6. The consequences of these observations are discussed in relation to 02 transfer across the placenta.

“…Though it is difficult to see the connexion, the amine oxidase content of the placenta appears to parallel the collagen content. The constant b for the relation of amine oxidase content to wet weight of rat's placenta, derived from the results of Thompson & Tickner (1949), is about 1*6.…”

Section: Margaret L R Harkness and R D Harknessmentioning

confidence: 99%

The growth of collagen in the foetus, placenta and foetal membranes of the rat

Harkness¹,

Harkness²

1955

. We have now made quantitative observations on the collagen content of the placenta, membranes and foetus of the rat during pregnancy. In all cases collagen content increased more rapidly than wet or dry weight. In the course of this work we also studied the quantity of amniotic fluid present at different times of pregnancy. METHODSAlbino rats ofthe local strain were used. Pregnancy was timed to ± 1 day by the method previously used (Harkness & Harkness, 1954b). Collagen was estimated by the method of Neuman & Logan (1950) with minor modifications (Harkness & Harkness, 1954a). Dryweightoftissueswas measured after drying over phosphorus pentoxide in vacuo. Total nitrogen was measured by the Kjeldahl procedure; digestion was done by the method of Chibnall, Rees & Williams (1943) and the ammonia was estimated after distillation into boric acid containing bromeresol green-methyl red indicator (Conway, 1947). The placenta and foetuses were homogenized in a small blendor of the Waring type. This did not break up all the individual bones of the older foetuses but we found that this did not appreciably affect the estimation. For both foetuses and placentas, judged by the hydroxyproline content of the residuum, the amount of collagen left after the usual aliquot was removed for analysis after autoclaving (Harkness & Harkness, 1954a) corresponded to the amount expected from the size of the aliquot, i.e. if any collagen in the bones remained undissolved after autoclaving the amount was too small to affect the results appreciably. Tyrosine estimations were made by the method of Medes (1932) on a number of samples and the quantity was small enough to be neglected. The hydroxyproline values have been accepted without correction for tyrosine.The animals were killed by a blow on the head and breaking the neck. The whole uterus was removed and weighed. The horns were opened and the foetuses removed with their placentas and membranes enclosing the amniotic fluid intact. The foetuses were then separated from the placentas, umbilical cords and membranes. These structures, together with the foetuses and empty uterus, were weighed and the weight of amniotic fluid was obtained by difference from the original 15 PHYSIO. CXXVIII