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M A Lazzari

Publications and source records attributed to M A Lazzari.

67 records · Page 4Linked to original sources
PubMed1983

The stimulatory effect of prostacyclin (PGI2) on isolated rabbit and rat aorta is probably associated to the generation of a thromboxane A2 (TXA2) "like-material".

Contractile responses to prostacyclin (PGI2) as well as the generation of PGI2 "like-material" in isolated aorta from rabbits and rats, were studied. PGI2 produced a biphasic response on thoracic aorta isolated from rabbits and rats, i.e. vasodilatation at low concentrations and distinct contraction at higher ones. The rabbit aortic arch responded with relaxation in the presence of a wide range PGI2 concentration. Inhibitors of prostaglandins and thromboxane A2 (TXA2) biosynthesis such as corticosterone, indomethacin, acetylsalicyclic acid, imidazole and L-8027, abolished the stimulatory effect of PGI2 in the thoracic aorta from rats and rabbits, while alpha adrenoreceptor blockers failed to modify the vasoconstricting influence. The basal generation of PGI2 "like-material" by thoracic aorta was significantly higher in rats than in rabbits. Thoracic aortic strips from rabbits diminished the antiaggregatory capacity of 5 ng/ml of PGI2 during 40 sec and the effect disappears within 2 min. The foregoing results suggest that in thoracic aorta from rats and rabbits the vasoconstrictor effect of PGI2 could be evoked by the production of an unstable constricting prostanoid with aggregatory capacity, presumably TXA2.

Adenosine Diphosphate↗
PubMed1982

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. In arteries from diabetic animals treated with insulin, PGI2 induced a biphasic contractile effect, which lay between that of normal controls and untreated diabetics. In addition the basal generation of "PGI2-like-material" by coronary arteries was significantly higher in the diabetic (141 +/- 0.2 pg/mg, mean +/- SEM) than in normal dogs (59 +/- 0.2 pg/mg). The present experiments demonstrate that the generation of "PGI2-like substance" is significantly increased in coronary arteries from diabetic dogs, but the same vessels are unable to respond to added authentic PGI2 with relaxation; on the contrary they react with a distinct positive contractile response.

Animals↗
PubMed1981

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. Less PGE-like material was found in the bathing solution during estrus than in metestrus or diestrus; the values obtained during proestrus were similar to those in estrus. PGI2 like material produced by chopped uterine tissue was greater during diestrus than in estrus. The initial isometric developed tension (IDI) and tension constancy varied depending of the stage of the sex cycle. Uteri from metestrous rats exhibited greater IDT and less % change with time than preparations from estrous or proestrous rats. The initial IDT, the tension change with time and contractile frequency correlate with the PGE-like material in the bathing solution during the 4 days of the sex cycle. There was no correlation with PGF-like material.

Animals↗
PubMed1980

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. Possible explanations underlying such finding are discussed.

Animals↗
PubMed1980

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. The initial effects (evoked by incubates of 30 minutes) were distinctly relaxing but those obtained with later incubates (60--150 minutes) stimulated clearly the resting basal tone of the arteries. The possibility that the human plasma might have an enzyme(s) able to transform prostacyclin into a more stable material with human antiaggregatory platelet function and bovine coronary contracting capacity is discussed.

6-Ketoprostaglandin F1 alpha↗
PubMed1980

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. The injection of 17-beta estradiol; progesterone or both diminished the production of the prostacyclin-like material by the uterus from ovariectomized rats. The already existing notion that ovarian steroids are able to regulate the synthesis of stable prostaglandins is discussed together with the present results suggesting in addition a depressive effect of sex hormones on the uterine PGI2 synthetase system.

Adenosine Diphosphate↗
PubMedDate not supplied

Effects of lopap on human endothelial cells and platelets.

Severe consumption coagulopathy has been detected in rats after Lopap (a prothrombin activator from Lonomia obliqua caterpillar bristles) infusion and in humans after accidental contact with L. obliqua bristles. However, platelet count and antithrombin (AT) levels were only modestly affected, suggesting that a different form of blood coagulation activation may be involved in this hemorrhagic syndrome. Here we describe that Lopap had no effect on aggregation of washed human platelets induced by several agonists, suggesting that it might not impair platelet function in vivo. AT was able to inhibit the amidolytic activity of thrombin generated by incubation of Lopap with prothrombin in a purified system, which may be different from that generated by the prothrombinase complex in vivo. The surface expression of both ICAM-1 and E-selectin but not of VCAM-1 was upregulated by Lopap in cultured HUVEC, suggesting that it may behave differently from other mediators, such as thrombin and tumor necrosis factor-alpha.

Animals↗