Low prostacyclin synthetase activity of fetal rat aorta. Progressive increase after birth

Deficient activity of prostacyclin stimulating plasma factor (PSPF) in newborns

The activity of PSPF was studied in 38 normal newborns. The production of 6-keto-PGF1 (PGI2 stable metabolite) after stimulation with cord blood plasma, 0.72 +/- 0.50 pmol/10(5) cells, was lesser than after stimulation with plasma from 2-3 years old children, 3.00 +/- 0.89 pmol/10(5) cells (p less than 0.01), or from adults, 7.74 +/- 5.00 pmol/10(5) cells (p less than 0.001). No differences were shown during neonatal period. The presence of a circulating inhibitor factor in newborns was dismissed by mixed cultures. The behaviour of neonatal plasma after consecutive stimulations with AA was similar to adult plasma response. We proved that newborns show a deficient capacity to stimulate PGI2, which is not due to circulating inhibitor factor, and we think that this deficiency is due to a weaker action of stimuli, rather than to an immaturity.

Nitrates do not affect prostacyclin formation by rat arteries: this is unrelated to increased vascular prostacyclin formation with age

The question of whether vasodilator nitrates act by releasing prostacyclin is controversial. Since the ability of blood vessels to form prostacyclin changes with age, we have investigated whether this may explain the discrepancies in the literature. It does not, since isosorbide dinitrate or glyceryl trinitrate incubated with rat aorta or vena cava from male Wistar rats had little or no effect on the release of prostacyclin, measured as 6-keto-PGF1 alpha. We confirm that the aorta produces substantially more prostacyclin than the vena cava. The arterial production of prostacyclin was greater in rats weighing 350-400 g than in those weighing 116-152 g, but the production by the veins was similar in both groups.

Human breast milk contains a factor which markedly stimulates aortic prostacyclin synthesis

Human breast milk has been shown to contain a potent factor which markedly stimulates the synthesis of prostacyclin by rabbit aorta. The stimulatory effect of colostrum was modest when compared to mature milk. This factor appears to be protein in nature with a molecular weight of less than 10 000. The main site of action of the factor appears to be on the conversion of arachidonic acid into prostacyclin. This factor might have a role in the optimal development of prostacyclin synthetic pathways which are not fully developed at birth.

Human breast milk stimulates prostaglandin synthesis in cultured human skin fibroblasts

Effect of human breast milk or its fractions on prostaglandin synthesis was investigated in cultured human skin fibroblasts. Prostaglandins released into the media were measured by radioimmunoassay. Incorporation of breast milk (2% level) into 10% fetal calf serum media (for 48 hours) stimulated the synthesis of 6-keto-PGF1 alpha (stable product of prostacyclin) by 800%. This stimulating effect of milk persisted after cold acetone extraction to remove phospholipids and potentiated further after dialysis. Stimulation by one of the commercial formulas (Similac) was less than 50% of the milk effect. Milk also stimulated PGE2 synthesis, although to a much lesser degree. These studies show for the first time that a) human breast milk contains potent factor(s) capable of influencing prostaglandin synthesis and suggest that b) these factors might have a role in the development of lipid synthetic pathways during early life.

Age-dependent changes in the synthesis and catabolism of 6 oxo PGE1 and other prostanoids by the rat kidney in vitro

Synthesis and catabolism of 6 oxo PGE1 was assessed in 100,000 g cell-free supernatant fractions of kidneys obtained from rats aged 20, 34 and 70 days. In addition the release of PGI2, TxA2 (measured as 6 oxo PGF1 alpha and TxB2, respectively), PGE2 and PGF2 alpha from kidney slices prepared from these three groups of rats was determined using specific radioimmunoassays. The conversion of PGI2 to 6 oxo PGE1 (but not 13,14 dihydro 15 oxo PGF2 alpha to 13,14 dihydro 15 oxo PGE2) was detected in supernatant fractions of kidneys from 20 day rats. Slices prepared from the kidneys of these animals spontaneously released significant amounts of three prostanoids (6 oxo PGF1 alpha greater than PGE2 greater than PGF2 alpha greater than TxB2 = 0). No formation of 6 oxo PGE1 from exogenous PGI2 was demonstrated in renal 100,000 g supernates from 34 and 70 day rats even though these supernates avidly oxidised 13,14 dihydro 15 oxo PGF2 alpha to 13,14 dihydro 15 oxo PGE2. In these animals the rank order of prostanoid release from kidney slices was PGE2 greater than 6 oxo PGF1 alpha greater than PGF2 alpha greater than TxB2 = 0. The catabolism of 6 oxo PGE1 is also age-dependent. In 20 and 34 day old rats 6 oxo PGE1 and PGE1 incubated with renal 100,000 g supernates undergo loss of biological activity as determined by the ability to inhibit ADP induced human platelet aggregation. In contrast, kidney 100,000 g supernates prepared from 70 day rats convert 6 oxo PGE1 to an unidentified metabolite with more potent anti-aggregatory activity. The possibility that 6 oxo PGE1 has a biological role in the developing rat kidney is discussed.

Influence of a vitamin E-deficient diet on prostacyclin production by mesometrial triangles and aortic rings from nondiabetic and diabetic pregnant rats

We investigated the effect of a vitamin E-deficient diet on the synthesis of prostacyclin in nondiabetic and diabetic pregnant rats. In both groups the diet reduced fetal growth and prostacyclin production by mesometrial triangles; it also increased serum lipid peroxides, which are known to inhibit prostacyclin synthesis. Independently of the diet, mesometrial triangles of diabetic rats produced more prostacyclin than those of control rats, whereas an opposite tendency was found in the aortic rings. Our model seems useful for fundamental and pharmacologic studies of the vascular pathology of pregnancy.