Thromboxane A2: effects on airway and vascular smooth muscle

Thromboxane A2, an unstable compound derived from prostaglandin G2, was generated by incubation of arachidonic acid with a suspension of human platelets. The activity of thromboxane A2 relative to that of prostaglandin H2 in causing contractions of a number of smooth muscle organs were as follows: rabbit aorta, 7-20; human umbilical artery, 9-60; and guinea pig trachea, 2-12. Intravenous injection of thromboxane A2 into anaesthetized quinea pigs was followed by a pronounced increase in the tracheal insufflation pressure, potency compared to prostaglandin H2, 31-45.

Formation and action of prostaglandin endoperoxides in the isolated human umbilical artery

The effects on the isolated human umbilical artery (HUA) of the recently isolated endoperoxide intermediates in prostaglandin (PG) biosynthesis, PGG2 and PGH2, were studied. Both endoperoxides were potent contractors of the artery strips, the threshold concentrations being 3 (1-4) ng/ml for PGG2 and 1 (1-12) ng/ml for PGH2, as compared with 200 (40-400) ng/ml for PGE2. The hemiacetal derivative of 8-(1-hydroxy-3-oxopropyl)-9,12L-dihydroxy-5,10-heptadecadienoic acid (thromboxane B2), a metabolite of PGG2, appeared in the bath medium indicating PG and thromboxane generation in the isolated HUA. The formation of thromboxane B2 was inhibited by indomethacin (8-40 mug/ml) and by eicosa-5,8,11,14-tetraynoic acid (ETA) (25 mug/ml), ETA also inhibited the contractile responses to both endoperoxides. The results support the view that local generation of PGs might be involved in the closure of the HUA at birth.

Prostaglandin biosynthesis in the human umbilical cord

The content of prostaglandins (PGs) in homogenates of arteries, connective tissue from human umbilical cords, and the capacity for biosynthesis of PGs in these tissues were studied. Lipid extracts were prepared and subjected to chromatography on silicic acid columns. PGs were eluted by ethyl acetate after elution with ethyl acetate-benzene (1:9) and determined by bioassay. For studies of the content of PGs, the cords were immediately frozen after delivery and homogenized in cold ethanol. Cords taken at vaginal deliveries contained amounts equivalent to approximately 700 ng prostaglandin E2/g dry weight and cords taken at caesarean sections about 450 ng/g. After homogenization and incubation of arteries in potassium phosphate buffer at 37 degrees C for 30 min the PG content increased from about 80 to 200 ng/g. Addition of arachidonic acid increased the biosynthesis fivefold. Indomethacin inhibited it. Most of the smooth muscle stimulating activity of the homogenated cords was due to prostaglandin E compounds, but smooth muscle stimulating material similar to prostaglandin F1alpha and F2alpha was also present. Prostaglandin E2 was conclusively identified by gas chromatography -- mass spectrometry. The findings are compatible with the view that local biosynthesis of PGs is very active in the human umbilical cord after delivery.

Reduction of the tone of the isolated human umbilical artery by indomethacin, eicosa-5,8,11,14-tetraynoic acid and polyphloretin phosphate

The effects of 2 prostaglandin synthetase inhibitors, indomethacin and eicosa-5,8,11,14-tetraynoic acid (ETA) and of the prostaglandin antagonist, polyphloretin phosphate (PPP), on the tone of the isolated human umbilical artery and on the responses of this preparation to 5-hydroxytryptamine (5-HG) and prostaglandin F2alpha (PGF2alpha) were investigated. Indomethacin (8 mug/ml), ETA (5 mug/ml) or PPP (40 mug/ml) reduced the tone of human umbilical arteries but had no influence on the responses to 5-HT. In these concentrations ETA and PPP but not indomethacin antagonized the action of PGF2alpha. When the concentration of indomethacin or PPP was increased 5-fold both 5-HT- and PGF2alpha-induced contractions were antagonized indicating a non-specific inhibition at these concentration levels. A 10-fold increase in the concentration of ETA had no antagonizing action on 5-HT-induced contractions suggesting a more selective inhibition of the PGF2alpha action than displayed by the other compounds. The effects on the tone of the human umbilical artery of the compounds studied might reflect inhibition of prostaglandin biosynthesis and/or antagonism of the action of formed prostaglandins. The findings are compatible with the view that intramural synthesis of prostaglandins contributes to the maintenance of the tone of the isolated human umbilical artery.

Effects and interactions of oxygen and prostaglandins on the tone of the isolated human umbilical artery

Prostaglandin E2 (PGE2) and prostaglandin F2alpha (PGF2alpha) were found to be equipotent contractors of the isolated human umbilical artery (HUA) in the concentration range 0.2-40 mug/ml. Prostaglandin E1 (PGE1) relaxed HUA at 0.1-3.0 mug/ml, whereas at 10-50 mug/ml contraction occurred. PGE2 was significantly more potent at a PO2 of 102 mmHg than at 27, 48 and above 400 mmHg. An increase in PO2 per se (27- greater than 400 mmHg) resulted occasionally in minor increases in the tone of the HUA. Such effects of oxygen had a lag period of 10-15 min. It is suggested that an increased formation of prostaglandins in the umbilical artery at birth is a more likely cause of the closure of the vessel than an increase in PO2.

High voltage QRS complexes in children with innocent, "vibratory" heart murmur

The electrocardiographic findings in 86 four-year-old children with innocent murmur of the so-called vibratory type are described. The electrical axis, the Q, R and S waves in the right and left precordial leads were compared with figures from the literature and with a control group of 4-year-old children without signs of somatic disease. The most significant findings were higher amplitudes of Q and R waves over the left precordium in children with vibratory murmur. Many children in this group had amplitudes of these waves exceeding accepted normal limits. There were no findings compatible with organic heart disease and the difference as compared to normal values and controls is probably a matter of variations in the position of the heart.

Double outlet right ventricle with spontaneously developing pulmonary outflow obstruction

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