Selective stimulation of PGE1-synthesis by soterenol in the isolated rat vas deferens is mediated by alpha adrenoreceptors.

The effects of soterenol on prostaglandin (PG) release by the isolated rat vas deferens were studied. Soterenol increased the amount of PGE1 released into the medium without affecting that of PGE2 or PGF2 alpha. The effect of soterenol was inhibited by phentolamine but not by butoxamine.

Contractile activity and prostacyclin generation in isolated coronary arteries from diabetic dogs.

The present study was aimed at determining the generation of "prostacyclin (PGI2)-like-material" in coronary arteries from normal and diabetic (pancreatectomized) dogs as well as the contractile responses to prostacyclin of preparations from normal, diabetic and insulin-treated diabetic animals. PGI2 produced a dose-dependent relaxation of coronary arteries from normal dogs. In contrast, those from diabetic animals were not related; indeed, at low concentrations PGI2 failed to evoke any effect but at higher ones it induced a distinct contraction.

Does hypoxia selectively stimulate the generation of prostaglandin E1 by the isolated rat uterus?

The contractile activity of uterine horns maintained for 90 to 120 minutes under normal oxygenation (carbogen or 100% O2) became undetectable. When in this condition the gassing was stopped one or two minutes later, regular phasic contractions appeared super-imposed on a small increment of the basal resting tone. Indomethacin and aspirin well known inhibitors of prostaglandin (PG) synthesis, blocked the contractile influence of hypoxia whereas neither tranylcypromine or imidazole were able to alter the stimulatory action.

Spontaneous motility and prostaglandin generation in rat uterine horns isolated during the estrous cycle.

Measurements were made of spontaneous contractions and release of prostaglandin E-and F-like material into the bathing medium by uterine horns isolated from rats in different stages of the sex cycle. After 70 min of contractile activity the preparations from estrous rats released more PGF than those from proestrous or metestrous rats. On the other hand, similar amounts of PGF-like material is generated by estrous and diestrous horns.

Prostacyclin (PGI2) and U-46619 stimulate coronary arteries from diabetic dogs and their action is influenced by inhibitors of prostaglandin biosynthesis.

Isolated coronary arteries from diabetic dogs presented different contractile response to U-46619 to prostacyclin (PGI2) and to arachidonic acid (AA) than those of normal dogs. The stimulatory effect of the synthetic endoperoxide analogue U-46619, was significantly higher in the diabetic condition than in preparations from normal animals. On the other hand, while PGI2 evoked a dose-dependent relaxation of normal coronary arteries, diabetic vessels were not relaxed by low concentration of PGI2 whereas higher ones produced a distinct constrictor effect.

Differences in the effects of acetylcholine on the vas deferens from normal and castrated rats. A participation of adrenergic mechanisms.

The epididymal portion of the rat vas deferens from normal and castrated rats exhibited clear differences regarding both the threshold and the maximal response to acetylcholine. Alpha adrenoceptor antagonists, hexamethonium and 6-hydroxydopamine diminished the effectiveness of low acetylcholine concentrations on normal and castrated preparations of the epididymal portion of isolated rat vas deferens, but did not influence the maximal response. On the other hand, desipramine enhanced the action of low concentrations of acetylcholine, both in threshold and maximal response; but failed to alter the reactivity to high concentrations of acetylcholine.

Chagasic sera alter the effects of ouabain on isolated rat atria. Participation of adrenergic mechanisms.

The effects of chagasic sera, containing an antibody (EVI antibody) which reacts with the plasma membrane of working myocardial cells, on "toxic" and "non-toxic" actions of ouabain upon isolated self beating or paced rat atria suspended in different media, were explored. Although ouabain produced a dose-dependent positive inotropic influence on atria suspended in Krebs-Ringer-bicarbonate (KRB) and in KRB plus normal human serum (KRB + NHS) it did not elicit any significant positive inotropic effect on atria beating in KRB plus EVI positive human chagasic serum (EVI(+)S). Additionally, EVI(+)S dose-response curves of classical signs of digitalis cardiac toxicity shifted to the left.

Inhibitory effects of some catecholamines on contractions of uterine strips isolated from estrous and spayed rats. Influence of endogenous and exogenous prostaglandins on the action of methoxamine.

Cumulative dose-response curves were produced for the effect of different adrenergic agonists on the contractions of uterine strips from natural estrous and ovariectomized rats. Isoproterenol, norepinephrine and phenylephrine inhibited uterine spontaneous contractions, whilst methoxamine stimulated them. The inhibitory influences were blocked by propranolol and the excitatory effect of methoxamine was abolished by phentolamine.

The effect of calcium and calcium antagonists on the electrically-evoked contractile activity of isolated rat ovaries.

The effects of different calcium concentrations and calcium antagonists on the mechanical activity evoked by electrical field stimulation of isolated rat ovaries, were explored. It was observed that the force of contraction augmented and the electrical threshold diminished as the (Ca2+)0 increased. On the other hand, in the presence of calcium antagonists (Verapamil, D-600 and MnCl2) as well as in calcium-free media, the force of contraction decreased and the electrical threshold augmented.

Inotropic effect of prostacyclin (PGI2) on isolated rat atria at different contraction frequencies.

The effects of a wide range of Prostacyclin (PGI2) concentrations on the Isometric Developed Tension (IDT) of isolated left auricles driven at different frequencies (0.8, 1.6 or 3.

Ovarian hormones inhibit the release of prostacyclin-like material from isolated rat uterus.

The influence of sex steroids on the production of prostacyclin (PGI2) like material by the isolated rat uterus incubated in a buffer medium was explored by monitoring its ability to inhibit ADP-induced platelet aggregation. Chopped uterine strips from rats in natural estrus can generate an unstable substance that inhibits platelet aggregation and suggest to be prostacyclin. This capacity was significantly enhanced in preparations from spayed animals.

Human plasma transforms prostacyclin (PGI2) into a platelet antiaggregatory substance which contracts isolated bovine coronary arteries.

Prostacyclin (PGI2) incubated in Human Platelet Rich Plasma (PRP); in Platelet Poor Plasma (PPP) or in Krebs-Ringer-Bicarbonate (KRB) during different periods of time on contractions of bovine coronary arteries and on the ADP platelet aggregative capacity of human PRP, were explored. It was documented that incubates in PRP or in PPP retain an antiaggregatory activity at higher levels and during a longer time than in KRB. On the other hand, PGI2 incubates in KRB exhibited only a relaxing activity on isolated bovine coronary arteries, whereas when incubated in PRP or in PPP presented a biphasic influence.

Human platelet rich plasma and human serum protects from inactivation the antiaggregatory capacity of prostacyclin-like material (PGI2) produced by the rat stomach fundus.

Prostacyclin (PGI2) synthetizing capacity of rat stomach fundus in Krebs-Ringer-Bicarbonate (KRB); human platelet rich plasma (PRP) or human serum (HS), was explored. The basal production of PGI2-like material was similar in the three media, suggesting the absence of any special substance in plasma or serum able to modify prostacyclin synthesis from tissue substrate. On the other hand it was also documented that in PRP and in HS the antiaggregatory activity of the PGI2-like material declined in its capacity less than 50% following 60 minutes of incubation at 37 degrees C, whereas it almost disappeared when incubated in KRB.

Contractile characteristics of fimbrial, isthmic, ampullar, and fimbrio-ampullar segments of isolated sow (Sus scrofa) oviducts as influenced by ovulation, adrenergic mechanisms, and prostaglandin E1.

Spontaneous contractile characteristics, as well as inotropic influences of norepinephrine (NE) and prostaglandin E1 (PGE1) on different sow oviductal segments isolated from preovulatory or early postovulatory period, were explored. Postovulatory fimbrial preparations contracted with higher intensity and slower frequency than preovulatory ones whereas the spontaneous motility of other regions were comparable at both stages. Norepinephrine (NE) depressed preovulatory ampullar and fimbrio-ampullar portions but stimulated fimbrial and isthmic segments.

Spontaneous contractile activity of isolated ovarian human vein. A dual influence of prostacyclin (PGI2).

The profile of spontaneous contractions as well as the influences of prostacyclin (PGI2) on the motility of human ovarian veins obtained during the estrogenic phase of the sex cycle were explored. The preparations exhibited a distinct phasic activity, which progressively decreased as isolation time progresses, dissapearing almost completely following more than two hours. PGI2 produced a biphasic influence on quiescent preparations.