Search PubMed⌕ Search

Biomedical subjects

F Guarner

Publications and source records attributed to F Guarner.

67 records · Page 4Linked to original sources

Effects of calcium and parathyroid hormone on prostacyclin synthesis by vascular tissue.

Prostacyclin generation by rat aortic rings was studied at different calcium concentrations. Extracellular calcium influenced prostacyclin synthesis, as reflected by the release of 6-keto-PGF1 alpha into the medium, in a concentration-dependent fashion. Calcium levels beyond the physiological range (1.12-1.25 mM unbound calcium) markedly stimulated 6-keto-PGF1 alpha production when compared with calcium-free solutions. On the other hand, addition of purified parathyroid hormone did not change 6-keto-PGF1 alpha production at any calcium concentration tested. These data suggest that parathyroid hormone has no direct effect on prostacyclin synthesis by vascular tissue, although it might influence prostacyclin generation through changes in extracellular calcium levels.

Animals↗

Renal function in fulminant hepatic failure: haemodynamics and renal prostaglandins.

Eighteen patients with fulminant liver failure were studied, 10 with normal renal function (group A) and eight with renal failure (group B, plasma creatinine greater than 200 mumol/l). Renal function was assessed by standard clearance techniques and patients in group B had a marked reduction compared with group A in both renal plasma flow and glomerular filtration rate. Raised plasma renin activity was observed in both groups, but levels in group B were significantly higher than in group A. Renal prostacyclin production was estimated by radioimmunoassay (RIA) of 6-keto-prostaglandin F1 alpha in urine, and the excretion rate was markedly increased in group A as compared with nine healthy controls, but was low in group B. The plasma concentrations of 6-keto-prostaglandin F1 alpha and thromboxane B2 were similar in groups A and B and were both significantly higher than in controls. Haemodynamic measurements showed a high cardiac output with low vascular resistance and mean arterial pressure within normal limits in both groups. The pulse pressure, however, was significantly higher in group B than in group A. In conclusion, patients in FHF with renal failure have marked renal vasoconstriction with increased plasma renin activity and reduced renal prostaglandin excretion indicative of an imbalance between vasoactive forces.

6-Ketoprostaglandin F1 alpha↗

Determination of 2,3-dinor-6-ketoprostaglandin F1 alpha in urine samples by liquid chromatography and radioimmunoassay.

A method for 2,3-dinor-6-ketoprostaglandin F1 alpha quantification based on high-performance liquid chromatography-radioimmunoassay is described. Samples are acidified to pH 3 and processed through C18 disposable cartridges. The prostanoids are eluted with methyl formate and further separated on a reversed-phase column using acetonitrile-acetic acid-triethylamine buffer (32:68). Studies of the effect of eluent pH were performed in order to optimize resolution and separation of 2,3-dinor-6-keto-PGF1 alpha from other prostanoids. Eluates were collected and assayed by radioimmunoassay using a heterologous system, with 6-keto-PGF1 alpha as radioligand and an antiserum with high cross-reactivity for 2,3-dinor-6-keto-PGF1 alpha. Sensitivity, precision and accuracy of the assay procedure are reported together with the validation of its specificity. The proposed method has been applied to the determination of this prostacyclin metabolite in human urine.

6-Ketoprostaglandin F1 alpha↗

Increased synthesis of systemic prostacyclin in cirrhotic patients.

Urinary excretion of two prostacyclin metabolites was investigated in 48 subjects: 8 controls and 40 cirrhotics (9 without ascites, 22 with ascites and preserved renal function, and 9 with functional renal failure). Urinary 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), believed to reflect renal prostacyclin production, was significantly increased in patients without ascites and in ascitic patients with preserved renal function, but cirrhotics with renal failure showed rates similar to controls. Excretion of 2,3-dinor-6-keto-PGF1 alpha (PGI-M), the major urinary metabolite of systemic prostacyclin, was increased in all groups of patients, including those with renal failure. A single dose of sulindac, a renal-sparing prostaglandin synthesis inhibitor, reduced PGI-M but not 6-keto-PGF1 alpha in 5 cirrhotic patients. This would be consistent with the predicted renal origin of the latter and the systemic origin of the former. Ascitic patients with high urinary excretion of PGI-M (above the median value) showed significantly lower mean arterial pressure and higher plasma renin activity and aldosterone than patients with excretion below the median. Urinary 6-keto-PGF1 alpha was higher in patients with low PGI-M. Finally, creatinine clearance corrected excretion of PGI-M, as an estimation of relative plasma levels correlates both with plasma renin activity and plasma aldosterone in the 31 subjects who presented with ascites. It is suggested that enhanced synthesis of systemic prostacyclin may influence hemodynamic changes in patients with liver cirrhosis. Overproduction of systemic prostacyclin in the absence of increased renal prostacyclin synthesis appears to be characteristic of patients with functional renal failure.

6-Ketoprostaglandin F1 alpha↗

Effect of spironolactone on renal prostaglandin excretion in patients with liver cirrhosis and ascites.

The effect of spironolactone on the urinary excretion of prostaglandins was studied in patients with liver cirrhosis and ascites. Patients were kept in bed and given a sodium-restricted diet for at least 4 days before spironolactone treatment was considered. Starting from the 5th day of protocol, patients were treated with this diuretic if their spontaneous weight loss had been less than 600 g during the 2 previous days. Patients were distributed in groups according to weight loss during the first 4 days on diuretic therapy: Group I (high responders), II (medium responders) and III (low responders). Group I patients showed higher basal values (4th day of protocol) of urinary sodium (P less than 0.02) and urinary 6-keto-PGF1 alpha (P less than 0.02) than the other patients, but there were no significant differences in the basal excretion rates of PGE2 nor TXB2 among the groups. The therapeutic requirement for spironolactone treatment in patients from Group I was delayed as compared with the other two groups (P less than 0.001) due to the fact that their spontaneous weight loss took place over a long period. For all patients, spironolactone administration produced a significant increase in 6-keto-PGF1 alpha excretion (P less than 0.01) without affecting significantly urinary elimination of PGE2 nor TXB2. A close relationship was found between the spironolactone-induced increments in urinary sodium and urinary 6-keto-PGF1 alpha excretion (r = 0.74, P less than 0.001). It is suggested that the ability of the kidney to synthetize prostacyclin can influence the natriuretic response to spironolactone therapy in patients with liver cirrhosis.

6-Ketoprostaglandin F1 alpha↗

Renal prostaglandins in cirrhosis of the liver.

Urinary prostaglandin excretion was studied in 42 patients with liver cirrhosis and in nine control subjects on restricted sodium intake and on bed rest. Creatinine clearance (CCr), sodium excretion (UNaV), plasma renin activity (PRA) and plasma aldosterone were also evaluated. Patients without ascites and ascitic patients without renal failure showed increased urinary excretion of immunoreactive 6-ketoprostaglandin F1 alpha (i6-keto-PGF1 alpha), prostaglandin E2 (iPGE2) and thromboxane B2 (iTXB2) when compared with controls, while immunoreactive PGF2a (iPGF2 alpha) levels did not differ from those in the control group. Patients with functional renal failure (FRF) presented a significant reduction of vasodilator prostaglandins but urinary excretion of iTXB2 was higher than in controls. On the whole, cirrhotic patients with higher urinary excretion of prostaglandins had normal or nearly normal PRA and aldosterone levels. i6-keto-PGF1 alpha and iPGE2 inversely correlated with PRA and aldosterone. The relationship between i6-ketoPGF alpha alpha and CCr was found to be highly significant in cirrhotic patients but not in the control group. On the other hand, iPGE2 significantly correlated with UNaV and with the fractional excretion of sodium (FENa). We concluded that: (a) enhanced renal prostaglandin synthesis in cirrhosis, inversely related to PRA and aldosterone, may be dependent on volume status; and (b) preserved renal function in these patients is associated with the ability to synthesize prostacyclin and PGE2.

6-Ketoprostaglandin F1 alpha↗

9 beta-methylcarbacyclin, a stable prostacyclin analogue, in prevention of platelet losses during charcoal haemoperfusion.

The effect of 9 beta-methylcarbacyclin, a stable analogue of prostacyclin, as a platelet protective agent, has been investigated during in-vitro charcoal haemoperfusion with fresh heparinized human blood, a model of progressive platelet damage. There were no platelet losses over 3 h perfusion after an initial bolus (1 microgram ml-1) of 9 beta-methylcarbacyclin (101.6 +/- s.e. 1.9% of initial value) whereas in the paired control circuit there was a significant reduction in the platelet level (73.5 +/- 4.1%, P less than 0.05). Prevention of rises in plasma thromboxane B2 by 9 beta-methylcarbacyclin confirmed the lack of platelet damage and a significant, but less marked, effect on white cell losses was observed. In a second series of experiments a bolus of 9 beta-methylcarbacyclin in one circuit was compared with prostacyclin infusion in the other which demonstrated that this prostaglandin analogue was as effective as prostacyclin and on the basis of these initial results it would merit clinical evaluation.

Blood Platelets↗

Effect of sulindac on prostaglandin excretion and renal function in cirrhotic patients with ascites.

The effect of sulindac, a nonsteroidal anti-inflammatory drug, on renal prostaglandin synthesis and renal function variables was investigated in six cirrhotic patients with tense ascites and marked sodium retention. We studied serum thromboxane (TXB2) production, urinary prostaglandin excretion (6-keto-prostaglandin F1 alpha and TXB2) and renal function before and after administration of a therapeutic dose of sulindac (400 mg). After treatment, no significant changes were observed in urinary prostaglandin excretion, serum creatinine concentration, urine volume, or urinary sodium and creatinine clearance, whereas the serum TXB2 concentration was reduced in 89%. In five patients systemic prostaglandins were inhibited, but renal excretion remained unchallenged. However, one patient showed marked reduction of urinary prostaglandins associated with a depression of renal function. The study suggests that sulindac could be a safe substitute for other nonsteroidal anti-inflammatory drugs in cirrhotic patients with ascites. Further pharmacological trials seem to be warranted.

Ascites↗

Cytoprotective effect of prostaglandins on isolated rat liver cells.

In vitro studies were carried out on isolated rat hepatocytes to examine further the proposed cytoprotective actions of prostaglandins (PG) using carbon tetrachloride (CCl4) as the toxic agent. Isolated hepatocytes, prepared by collagenase, were cultured in Leibowitz-15 medium. Following preincubation, CCl4 (300 or 150 micrograms/ml) was added to the hepatocytes. Treatment with Indomethacin (INDO), 16, 16-dimethyl-PGE2(PGE2) and prostacyclin (PGI2) was assayed in the cultures. Cell damage was measured by lactic dehydrogenase (LDH) release. 6-keto-PGF1 alpha was measured in the supernatant by direct radioimmunoassay. The results showed PGI2 (30.0 ng/ml) treatment 30 min after CCl4 (300 micrograms/ml) addition to be highly protective (p less than 0.001 versus CCl4 control). PGE2 (3 ng/ml) showed similar protection (p less than 0.001). INDO (2 micrograms/ml) following CCl4 (150 micrograms/ml) demonstrated increased cell death (p less than 0.001). INDO (0.5 micrograms/ml) reduced 6-keto-PGF1 alpha production (p less than 0.05). Low dose ethanol (1.5 micrograms/ml) increased 6-keto-PGF1 alpha production (p less than 0.05). Ethanol (1.5 micrograms/ml), added to stimulate endogenous PG production, was cytoprotective when added prior to CCl4 (p less than 0.01). This protection was suppressed by INDO. Ethanol added after CCl4 was not protective. We conclude that exogenously added PGI2 and PGE2 are cytoprotective in this in vitro model and that endogenous PG production may play a protective role in the initial stages of cellular damage.

Animals↗

Intracerebroventricular infusion of sodium chloride-rich artificial cerebrospinal fluid in rats induces natriuresis and releases an inhibitor of prostaglandin synthesis.

Urinary sodium excretion in anaesthetized rats subjected to high-sodium artificial cerebrospinal fluid (CSF) infusion into the lateral brain ventricle, was significantly higher than in rats infused with normal-sodium CSF. Urinary immunoreactive 6-ketoprostaglandin F1 alpha, the stable derivative of prostacyclin, was significantly reduced in the high-sodium CSF group, as compared with the normal-sodium CSF group. When dog aortic endothelium was incubated in the presence of plasma, endothelial prostacyclin production was found to be inhibited by plasma from rats infused with high-sodium CSF compared with the effect of plasma from the rats infused with normal-sodium CSF. Our results indicate that intracerebroventricular infusion of high-sodium CSF induces a natriuretic response and is associated with the appearance of a humoral factor which blocks prostacyclin biosynthesis.

6-Ketoprostaglandin F1 alpha↗

Reduction by prostacyclin of acetaminophen-induced liver toxicity in the mouse.

The effect of prostacyclin on acetaminophen-induced liver injury has been investigated in the mouse. Two structurally unrelated thromboxane synthetase inhibitors, OKY 1581 and benzyl imidazole, were also examined in order to investigate the role of the prostacyclin-thromboxane balance in the development of hepatic lesions. Whereas prostacyclin or OKY 1581 given shortly after acetaminophen prevented mortality and reduced liver necrosis, as assessed by serum ALT activity and histology, benzyl imidazole was only effective if given prior to acetaminophen. Acetaminophen overdose resulted in an enhanced prostaglandin and thromboxane generation by liver homogenates. While OKY 1581 inhibited thromboxane production by the liver homogenates, prostacyclin synthesis was increased. Pretreatment with the cyclooxygenase inhibitor indomethacin blocked both the increase in prostacyclin generation and the protective effect of OKY 1581. Benzyl imidazole inhibited the synthesis of thromboxane but did not enhance prostacyclin production. In addition, the protective effect of benzyl imidazole was unaltered by indomethacin pretreatment. Furthermore, whereas benzyl imidazole interfered with hepatic drug metabolism, as assessed by prolongation of the pentobarbitone sleeping time, prostacyclin and OKY 1581 were without activity. Prostacyclin treatment can prevent acetaminophen-induced liver necrosis in mice. Enhanced prostacyclin synthesis by the selective thromboxane synthetase inhibitor OKY 1581 also exerts a protective role in this model.

Acetaminophen↗

Ethanol feeding aggravates morphological and biochemical parameters in experimental chronic pancreatitis.

BACKGROUND AND AIMS: Instillation of trinitrobenzene sulfonic acid (TNBS) into the rat pancreatic ducts induces morphological changes resembling human chronic pancreatitis. In humans, alcoholism is commonly associated with chronic pancreatitis, but ethanol feeding fails to induce pancreatitis in experimental animals. We hypothesized that ethanol would manifest its pathogenetic effects on a duct-injured pancreas. METHODS: Chronic pancreatitis was induced in rats by instillation of TNBS into pancreatic ducts. Thereafter, rats were fed a normal chow diet with or without ethanol supplementation. Control rats received vehicle and a normal diet. A separate group of vehicle-treated rats were also fed with ethanol. At 2 and 4 weeks pancreata were excised and processed for morphological examination or for biochemical assays. From crude homogenates, protein and hydroxyproline were quantified. After sonication, homogenates were also assayed for amylase and DNA. An oral glucose tolerance test was performed on the fourth week. RESULTS: TNBS induced chronic fibrogenic pancreatitis that was associated with a reduction in pancreatic weight, DNA, protein and amylase as compared to control rats. Ethanol feeding to TNBS-treated animals slowed weight gain, increased fasting glucose and impaired glucose tolerance test. Larger areas of gland atrophy were observed with a striking disruption of the normal architecture of the islets. Ethanol accelerated pancreatic involution and collagen deposition as measured by total amylase, protein, DNA and hydroxyproline content. CONCLUSIONS: In TNBS chronic pancreatitis, active fibrogenesis is associated with progressive atrophy of glandular elements. Morphological and biochemical parameters are aggravated by sustained ethanol intake.

Amylases↗