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Biomedical subjects

N A Terragno

Publications and source records attributed to N A Terragno.

At least 37 records · Page 2Linked to original sources
PubMed1977

Dual effects of bradykinin on prostaglandin metabolism: relationship to the dissimilar vascular actions of kinins.

Generation of a prostaglandin of the F series by bovine mesenteric veins in response to bradykinin may depend on increased synthesis of PGE and conversion of the latter to PGF after activation of PGE 9-ketoreductase by the kinin. The prostaglandin then mediates the constrictor action of bradykinin on the bovine mesenteric vein. A high speed supernatant (HSS) fraction of bovine mesenteric blood vessels contains the highest activity of PGE 9-ketoreductase. Incubation of PGE2 with HSS at 37 degrees C in the presence of a NADPH generating system resulted in time-dependent conversion of PGE2 to PGF2alpha. Bradykin (0.01mM) more than doubled conversion of PGE2 to PGF2alpha by the PGE 9-ketoreductase obtained from mesenteric veins whereas the kinin had little effect on enzymic activity of the HSS fraction of mesenteric arteries. However, after inhibition of kininase catabolism, bradykinin increased PGE 9-ketoreductase activity of arteries and veins to the same degree. Prostaglandin release from veins by bradykinin appears essential to contraction of mesenteric venous strips evoked by the polypeptide as indomethacin treatment abolished this effect. PGE 9-ketoreductase may be an important prostaglandin regulatory mechanism of the vascular wall whereby the functional consequences of changes in rates of prostaglandin synthesis are governed by determining the ratio of PGE to PGF within vascular tissue. Constriction of bovine mesenteric veins evoked by bradykinin may, therefore, depend on increased prostaglandin synthesis and conversion of newly formed PGE to PGF, both steps being affected by the kinin.

Alcohol Oxidoreductases↗
PubMed1977

Synthesis of prostaglandins by the ductus arteriosus of the bovine fetus.

Previous studies demonstrated that prostaglandins are local or tissue hormones which can be released from blood vessel walls. In the present study, we investigated the capacity of bovine ductus arteriosus to synthetize prostaglandins in vitro. After incubation of slices of ductus arteriosus in Krebs' solution with (1-14C) arachidonic acid for 3 hours, more than 40% of the radiolabeled material recovered from the incubating medium were metabolites of arachidonic acid. The major product was indistinguishable from 6 keto-PGF1alpha as determined by its chromatographic motility and resistance to alkaline conversion to PGB. The PGI2 synthetic capacity of the ductus arteriosus, as revealed by the predominance of its major metabolite 6 keto-PGF1alpha, suggests that this metabolic pathway of arachidonic acid may contribute to the hemodynamic changes occurring during fetal life and at birth.

Animals↗
PubMed1977

Contribution of prostaglandins to the renal circulation in conscious, anesthetized, and laparotomized dogs.

The effects of an inhibitor of prostaglandin (PG) synthetase, indomethacin, were studied on renal blood flow (RBF) and mean aortic blood pressure (MABP) and related to changes in concentrations of PGs in renal venous blood under widely different experimental conditions. Although levels of PGE-like material ("PGE") in renal venous blood of the chloralose-anesthetized-laparotomized dog were 8-fold greater than in conscious dogs, viz., 0.39 vs. 0.05 ng/ml of blood, respectively, RBF and MABP were similar for each group. Indomethacin in doses as high as 10 mg/kg, iv, affected neither RBF, MABP, nor PG levels either in the conscious dog or in the anesthetized dog. However, in the anesthetized-laparotomized dog, smaller doses of indomethacin (2 mg/kg, iv) decreased RBF by more than 40% and increased MABP by 15%. This was associated with a decline in concentration of renal venous PGs to those levels observed in conscious dogs. The principal renal PG varied according to the experimental conditions. The venous levels of "PGF" were greater than "PGE" in conscious dogs, whereas in acutely stressed dogs the renal venous concentrations of "PGE" were more than 2-fold those of "PGF". Plasma renin activity was highly correlated with "PGE" levels in renal venous blood, but not with "PGF" levels. Thus, in the acutely stressed dog, the renal circulation is supported by a major PG component, withdrawal of which results in a decline in RBF. In contrast, in the conscious dog at rest, renal PGs do not appear to contribute significantly to RBF. The significance of the small basal release of PGs into the renal venous effluent of the conscious dog, which is not affected by indomethacin, remains to be determined.

Anesthesia↗
PubMed1977

Role of naturally occurring vasoactive principles in hypertension. State of the art.

Hypertension may result from excessive activity of one or more components of the blood pressure-elevating system. These include the adrenergic nervous system, the renin-angiotensin axis, and mineralocorticoids (aldosterone), which potentiate each other, reinforcing their effects on renal hemodynamics and electrolyte transport and thereby affecting extracellular fluid volume, vascular tone, and reactivity. We consider of no less importance in the genesis of hypertension the failure of one or more components of the blood pressure-lowering system: the kallikrein-kinin system, prostaglandin, or one or more lipids associated with the renomedullary interstitial cells. As a corollary of this hypothesis, if one assumes tonic activity of these opposing blood pressure-regulating systems, in the case of a deficiency of the vasodepressor system, hypertension should result. That is, unopposed activity of the pressor system should be sufficient to increase blood pressure without an increase in the "basal level" of its activity. Hypertension, then, may be considered to result from either uncompensated deficiencies or excesses, which may be relative or absolute, of one or more components of the vasodepressor and vasopressor systems.

Animals↗
PubMed1976

Prostaglandins as determinants of vascular reactivity.

Prostaglandins are primarily local or tissue hormones that have their effects at, or near to, the site of synthesis. Some blood vessels synthesize prostaglandins intramurally, where their local release influences vascular tone and reactivity. Endogenous prostaglandins (primarily prostaglandin E2 (PGE2) participate in the regulation of vascular reactivity by opposing the vasoconstrictor and antinatriuretic actions of circulating pressor hormones; and by braking the release of norepinephrine from vasoconstrictor nerves. The proposal that one or more prostaglandins affect vascular reactivity is supported by the following observations: enhanced vascular reactivity to pressor stimuli occurs in organs with low basal rates of prostaglandin synthesis and after inhibition of prostaglandin synthetase in organs with high biosynthetic capacity; and exogenous PGE2 reversibly inhibits the vasoconstrictor activity of pressor stimuli.

Angiotensin II↗
PubMed1976

Renal prostaglandins.

1. Renal prostaglandins act primarily as local hormones, having their effects at, or near to, sites of synthesis. PGE2 is a major determinant of renal vascular reactivity; it opposes the vasoconstrictor and natriuretic actions of pressor hormones and brakes the release of noradrenaline from adrenergic nerves. In the unanaesthetized rabbit prolonged inhibition of prostaglandin synthesis results in hypertension. In the rat, however, renal prostaglandins augment pressor stimuli. 2. Basal efflux of renal prostaglandins is positively correlated with blood flow to the inner cortex and medulla. Those stimuli which increase renal medullary blood flow do so primarily by activating prostaglandin synthetase. 3. Kinins increase prostaglandin synthesis which action modifies the renal effects of kinins. Thus, one or more renal prostaglandins contribute to the renal vasodilator action of bradykinin and mediate its effect on excretion of water as well as possibly attenuating the natriuretic action of the polypeptide. Kinins in addition to stimulating prostaglandin synthesis may determine the principal product of synthetase by regulating the enzyme PGE 9-ketoreductase, which converts PGE to PGF. The coupling of these systems within the kidney appears unique--prostaglandins mediate some of the actions of kinins and modulate others, whereas they depend on the intrarenal generation of kinins to set their level and type of activity.

Animals↗
PubMed1975

The actions of bradykinin and eledoisin in the canine isolated kidney: relationships to prostaglandins.

1. The effects of two vasodilator polypeptides, bradykinin and eledoisin, were studied in isolated blood-perfused canine kidneys before and after administration of indomethacin, an inhibitor of prostaglandin synthesis, Bradykinin, but not eledoisin, releases renal prostaglandins. 2. Before administration of indomethacin, bradykinin decreased urinary osmolality and increased free qater clearance, whereas eledoisin did not affect the excretion of solute-free water. After administration of indomethacin, the renal vasodilator action of bradykinin was reduced but the vasodilator action of eledoisin was unaffected. 3. Fractional excretion of sodium was not affected by bradykinin before but was increased after administration of indomethacin. Reduction in glomerular filtration rate contributed to changes in sodium excretion produced by bradykinin and eledoisin. 4. The release of prostaglandins from the kidney by bradykinin amplifies the renal vasodilator action of the kinin and possibly mediates its effect on excretion of solute-free water.

Animals↗
PubMed1975

Prostaglandin synthesis by bovine mesenteric arteries and veins.

Prostaglandins (PG) were synthesized at similar rates by bovine mesenteric arteries and veins; viz., ca. 200 ng/g wet weight after one hour of incubation. After synthesis, PGE and PGF compounds were released from slices of arteries and veins into the incubating medium; PG were not detected in the walls of these blood vessels. Arachidonic acid, the precursor to PGE-2 and PGF-2-alpha, did not affect PG synthesis, whereas meclofenamate, an aspirin-like agent, decreased synthesis in arteries and veins by 90%. The PG biosynthetic capacity of these blood vessels is high, as indicated by greater than 20% conversion of (1-14C)-arachidonic acid to radiolabeled PG. Under control conditions in both arteries and veins, synthesis of PGE-2 exceeded that of PGF-2-alpha twofold. Bradykinin selectively increased the synthesis of a PGE-like substance in arteries and of a PGE-like substance in veins.

Animals↗