PubMed Health⌕ Search

Biomedical subjects

J F Brien

Publications and source records attributed to J F Brien.

At least 55 records · Page 3Linked to original sources
PubMed1989

Activity of alcohol dehydrogenase and aldehyde dehydrogenase in maternal liver, fetal liver and placenta of the near-term pregnant ewe.

The activity of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) was determined in the near-term pregnant ewe. There was little ADH activity in fetal liver (4.4%) and placenta (0.2%) compared with maternal liver. Low KM (microM acetaldehyde) ALDH activity was similar in the three tissues. High KM (mM acetaldehyde) ALDH activity was less in fetal liver (57%) and placenta (16%) compared with maternal liver. These data and the pharmacokinetics of ethanol and its proximate metabolite, acetaldehyde, in the near-term pregnant ewe indicate that ethanol elimination from the maternal-fetal unit is regulated primarily by maternal hepatic ADH-catalyzed biotransformation of ethanol, and low KM ALDH activity in the fetal liver and placenta protects the fetus from exposure to ethanol-derived acetaldehyde, which is produced primarily in the maternal compartment.

Acetaldehyde↗
PubMed1988

A facile, reliable method for staining blood vessel endothelium.

A modification of the silver-based stain for outlining endothelial cell borders of rabbit aorta is described. The present method uses ammonium sulfide in place of exposure to light to develop the stain. Rabbit aortic rings were sequentially immersed in 280 mM dextrose, 15 mM silver nitrate, 280 mM dextrose, dilute ammonium sulfide, and 280 mM dextrose solutions. They were then cut open and mounted on microscope slides with glycerin jelly. The procedure is rapid, easily mastered, and suited for use in most pharmacology laboratories. The resulting preparations can be viewed under reflected or transmitted light.

Animals↗
PubMed1988

Patterns of isosorbide dinitrate and glyceryl trinitrate metabolites formed by selected segments of the rabbit gastrointestinal tract.

Homogenates of selected segments of the rabbit gastrointestinal tract (GIT) were studied for their ability to biotransform isosorbide dinitrate (ISDN) and glyceryl trinitrate (GTN) to their mono- and di-nitrate metabolites, respectively. In addition, preferential formation of certain metabolites was investigated by examination of the patterns of metabolites formed by the various homogenates. After a 30-min incubation of ISDN with GIT homogenates (pH 7.4, 37 degrees C), the percent disappearance of ISDN and the ratio of isosorbide-2-mononitrate (2-ISMN) to isosorbide-5-mononitrate (5-ISMN) were as follows: stomach, 32%, 0.8; duodenum, 65%, 0.1; jejunum, 59%, 0.2; ileum, 38% , 1.2; cecum, 33%, 2.7; and colon, 32%, 3.4. After a 5-min incubation of GTN with GIT homogenates, the percent disappearance of GTN and the ratio of glyceryl-1,3-dinitrate (1,3-GDN) to glyceryl-1,2-dinitrate (1,2-GDN) were as follows: duodenum, 54%, 0.65; ileum, 73%, 0.68; and colon, 61%, 0.17. Incubation of 2 x 10(-7) M ISDN with mucosal and muscularis homogenates of duodenum, jejunum, and ileum resulted in significant losses of ISDN with an equimolar formation of the mononitrate metabolites. Most of the metabolic activity for ISDN resided in the mucosal layer of each section. The ratio of 2-ISMN to 5-ISMN varied in each section (stomach to colon) and cross section (mucosal versus muscularis) of the GIT. We conclude that the metabolism of ISDN and GTN by the GIT may contribute to the high clearance of these organic nitrates, and the low oral bioavailability of ISDN. Also, multiple mechanisms appear to be involved in the biotransformation of ISDN and GTN in the rabbit GIT.

Animals↗
PubMed1988

Nitric oxide-induced vasodilation of organic nitrate-tolerant rabbit aorta.

It is postulated that the organic nitrate vasodilator agents, including glyceryl trinitrate (GTN) and isosorbide dinitrate (ISDN), are prodrugs, such that biotransformation to the active inorganic metabolite, nitric oxide (NO), occurs prior to the onset of vasodilation. Furthermore, it is proposed that organic nitrate tolerance in vascular tissue involves decreased formation of NO. To test this latter hypothesis, we examined vasodilation induced by NO, GTN, and ISDN in non-tolerant, GTN-tolerant, and ISDN-tolerant rabbit aortic rings (RARs). Isolated RARs were contracted submaximally with phenylephrine; the time of onset of relaxation and percent relaxation of tissue were determined in response to NO (0.3 microM), GTN (0.03 microM), and ISDN (0.12 microM) before and after a 1-h treatment with 500 microM GTN, 500 microM ISDN, or buffer only. The data demonstrated that the response to NO was not changed in GTN-tolerant and ISDN-tolerant tissues, in which there was virtually no GTN-induced or ISDN-induced relaxation. These results are consistent with the postulate that organic nitrate vasodilator drugs must undergo biotransformation to NO before vasodilation can occur and that the mechanism of organic nitrate tolerance involves decreased formation of NO.

Animals↗
PubMed1988

Mechanism of glyceryl trinitrate-induced vasodilation. I. Relationship between drug biotransformation, tissue cyclic GMP elevation and relaxation of rabbit aorta.

This study was conducted to test the hypothesis that biotransformation of glyceryl trinitrate (GTN) is involved in GTN-induced relaxation of vascular smooth muscle. The temporal relationship between GTN biotransformation, elevation of cyclic GMP content and vasodilation in rabbit aortic strips (RAS) was determined. Isolated RAS were contracted submaximally with phenylephrine, and then were incubated with 0.62 microM [3H]GTN in a 30-sec time course study. GTN-induced relaxation (inhibition of phenylephrine-induced tone) of RAS was monitored; tissue cyclic GMP content was measured by radioimmunoassay; and GTN, glyceryl-1,2-dinitrate (1,2-GDN) and glyceryl-1,3-dinitrate (1,3-GDN) concentrations in RAS were measured by thin-layer chromatography and liquid scintillation spectrometry. There was time-dependent biotransformation of GTN to GDN by the RAS and a time-dependent increase in cyclic GMP content in the RAS. Statistically significant (P less than .05) biotransformation of GTN and elevation of cyclic GMP content in the tissue occurred at 10 sec, whereas the onset of GTN-induced relaxation of RAS occurred at 12 sec. During the tissue biotransformation of GTN, there was preferential formation of 1,2-GDN compared with 1,3-GDN, with 1,2-GDN/1,3-GDN ratio of 3.0/1 at 10 sec, 5.3/1 at 20 sec and 5.8/1 at 30 sec. The results of this study are consistent with the hypothesis that GTN is a prodrug, such that biotransformation to an active metabolite is involved in GTN-induced relaxation of vascular smooth muscle. The data also indicate that the mechanisms of GTN biotransformation and GTN-induced activation of guanylate cyclase may be related intimately.

Animals↗
PubMed1988

Mechanism of glyceryl trinitrate-induced vasodilation. II. Lack of evidence for specific binding of GTN to bovine pulmonary vein.

Radioligand binding studies were conducted to test the hypothesis that specific receptor sites for glyceryl trinitrate (GTN) exist in vascular smooth muscle. The radioligand, [3H]GTN (9.98 Ci/mmol), was incubated with whole homogenate or subcellular fractions (10,000 X g pellet, 100,000 X g pellet and 100,000 X g supernatant) of bovine pulmonary vein (BPV) at 4 degrees C, 37 degrees C or room temperature. After incubation for 5, 15, 30 or 60 min, unbound and bound ligand were estimated by physical separation and liquid scintillation spectrometry. Separation of bound from free ligand was accomplished by vacuum filtration, centrifugation, equilibrium dialysis, gel filtration or precipitation. No evidence of specific binding of [3H]GTN to BPV whole homogenate or any subcellular fraction was observed. The viability of the BPV preparations was verified by demonstrating specific binding of [3H]nitrendipine to the 100,000 X g pellet. To ensure that the ligand was present throughout the incubation procedure in sufficient concentration to detect specific binding, the ability of BPV whole homogenate and subcellular fractions to biotransform GTN to glyceryl dinitrate was measured. After 60-min incubation at 37 degrees C, greater than 95% of the GTN added was unaltered; at 90 min, more than 83% of the radioactivity was associated with GTN. Our data are interpreted as not supporting the concept of a GTN receptor in BPV.

Animals↗
PubMed1987

Disposition of acute, multiple-dose ethanol in the near-term pregnant ewe.

The disposition of ethanol and its proximate metabolite, acetaldehyde, was determined in seven conscious instrumented pregnant ewes (127 to 132 days of gestation; term, 147 days) for intravenous infusion of four dosages of 0.5 gm ethanol/kg maternal body weight, administered over 5 hours to the mother. The maternal and fetal blood had ethanol concentrations that were maximal at 5 hours and were virtually identical during the 24-hour study. There was delayed transfer of ethanol into the amniotic and allantoic fluids during the dosing period, followed by higher ethanol concentrations in these fluids during the elimination phase compared with fetal blood. The ethanol elimination rate was similar for the four biologic fluids. Acetaldehyde concentrations in the four fluids were a thousandfold less than the respective ethanol concentrations. The maternal blood acetaldehyde concentration was greater than that in fetal blood. The data indicate that for a binge-type drinking episode during near-term pregnancy, there is unimpeded bidirectional placental transfer of ethanol between the mother and the fetus; the amniotic fluid surrounding the fetus is a reservoir for ethanol in utero; elimination of ethanol from the maternal-fetal unit is regulated by maternal hepatic biotransformation of ethanol; and there is appreciable acetaldehyde-oxidizing capacity in the maternal liver and at extrahepatic sites.

Acetaldehyde↗
PubMed1987

Distribution of amiodarone and its metabolite, desethylamiodarone, in human tissues.

The distribution of the antiarrhythmic drug amiodarone and its principal lipophilic metabolite, desethylamiodarone, was determined in postmortem tissues of six patients who received amiodarone therapy (treatment period, 6-189 days; total dose, 4.8-127.0 g). Amiodarone concentration was highest in liver, lung, adipose tissue, and pancreas, followed by kidney, heart (left ventricle), and thyroid gland, and lowest in antemortem plasma. There was no measurable amiodarone in brain (less than 1.0 microgram/g). Desethylamiodarone concentration was highest in liver and lung, followed by pancreas, adipose tissue, kidney, heart, thyroid gland, and brain, and lowest in plasma. For most patients, the desethylamiodarone concentration was higher than the amiodarone concentration in liver, lung, kidney, heart, thyroid gland, and brain, whereas the parent drug concentration was higher than the metabolite concentration in adipose tissue, pancreas, and plasma. Tissue amiodarone and desethylamiodarone concentrations appeared to be related more closely to the total dose of amiodarone than to their respective plasma concentrations. One patient died of apparent amiodarone-induced pulmonary toxicity after an 18-day period of pharmacotherapy. Clinical evidence of pulmonary dysfunction appeared at 15 days after the initiation of amiodarone therapy, and the patient died at 23 days. Histologic assessment of a lung necropsy specimen revealed acute alveolar interstitial damage. This case represents the earliest reported incident of amiodarone-induced pulmonary toxicity.

Adipose Tissue↗
PubMed1987

The role of fetal urinary excretion in the transfer of ethanol into amniotic fluid after maternal administration of ethanol to the near-term pregnant ewe.

The objective of this study was to determine whether fetal urinary excretion is a major route of ethanol transfer into the amniotic fluid surrounding the fetus following maternal administration of ethanol. Conscious instrumented pregnant ewes between 130 and 137 days' gestation (term, 147 days) with (n = 3) or without (n = 3) a catheter in the fetal bladder were administered 1 g ethanol/kg maternal body weight as a 1-h maternal intravenous infusion. Maternal blood, fetal blood, and amniotic fluid samples were collected at selected times, and fetal urine was collected continuously from the bladder-cannulated fetus during the 14-h study for the determination of ethanol concentrations. Fetal urinary excretion of ethanol occurred, and the total amount of ethanol excreted represented 0.30 +/- 0.07 (SD)% of the maternal ethanol dose. The renal clearance of ethanol by the fetus was 0.43 +/- 0.06 mL/min. The pharmacokinetics of ethanol in the maternal-fetal unit and the amniotic fluid for the bladder-cannulated fetal preparation were similar to the data for the nonbladder-cannulated preparation. The data indicate that fetal urinary excretion of ethanol is a secondary route of ethanol transfer into the amniotic fluid. It would appear that diffusion of ethanol across membranes from the maternal and fetal circulations is a major route of ethanol transfer into this intrauterine compartment.

Amniotic Fluid↗
PubMed1987

A comparative study of glyceryl trinitrate biotransformation and glyceryl trinitrate induced relaxation in bovine pulmonary artery and vein.

Recent evidence supports the hypothesis that the mechanism by which glyceryl trinitrate induces relaxation of vascular smooth muscle involves the biotransformation of glyceryl trinitrate. This study was conducted to determine if there was a direct correlation between the capacity of vascular smooth muscle preparations to biotransform glyceryl trinitrate and their sensitivity to the relaxant effect of this organic nitrate. Isolated bovine pulmonary arteries and veins were contracted submaximally and cumulative dose-response relationships to glyceryl trinitrate were obtained; the vein was approximately 10 times more sensitive than the artery to glyceryl trinitrate induced relaxation. In a separate series of experiments, these vascular tissues were contracted submaximally and incubated with 0.5 microM [14C]glyceryl trinitrate for 2 min, during which glyceryl trinitrate induced relaxation was monitored. At 2 min, tissue samples were taken for determination of glyceryl trinitrate and glyceryl-1,2- and 1,3-dinitrate content by thin-layer chromatography and liquid scintillation spectrometry. Biotransformation of glyceryl trinitrate to glyceryl dinitrate occurred concomitantly with relaxation of these blood vessels. The concentration of glyceryl dinitrate in the vein was significantly less than that in the artery (p less than or equal to 0.05), even though significantly greater relaxation of the vein than the artery was observed (p less than or equal to 0.05). From these data, a simple linear relationship between glyceryl trinitrate biotransformation and relaxation is not apparent.

Animals↗
PubMed1987

Sex- and species-related differences in the biotransformation of isosorbide dinitrate by various tissues of the rabbit and rat.

The biotransformation of isosorbide dinitrate (ISDN) by various tissues of the rabbit and rat was examined. Incubation of 2 X 10(-7) M ISDN at 37 degrees C with tissue homogenates of liver, lung, kidney, intestine, skeletal muscle, aorta, and erythrocytes from the rabbit and rat resulted in a significant disappearance of ISDN after a 30-min incubation (also, 5-min incubation for liver). The disappearance of ISDN in each tissue homogenate was accompanied by an equimolar production of the mononitrate metabolites, isosorbide-2-mononitrate (2-ISMN) and isosorbide-5-mononitrate (5-ISMN), with the exception of liver homogenates where the loss of ISDN could not be accounted for by mononitrate formation. The relative rate of ISDN disappearance in various tissue homogenates was for the male rabbit, liver greater than lung approximately intestine greater than kidney greater than erythrocytes approximately skeletal muscle approximately aorta; for the female rabbit, liver greater than kidney approximately lung approximately intestine greater than erythrocytes approximately skeletal muscle approximately aorta; and for the male rat, liver greater than intestine greater than erythrocytes greater than skeletal muscle greater than lung approximately kidney. A sex difference in the percent disappearance of ISDN was observed in homogenates of lung and intestine from male and female rabbits. In addition, a sex difference in the ratio of metabolite (2-ISMN/5-ISMN) formed by denitration of ISDN was seen in homogenates of lung, skeletal muscle, and erythrocyte lysate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Disposition of ethanol and activity of hepatic and placental alcohol dehydrogenase and aldehyde dehydrogenases in the third-trimester pregnant guinea pig for single and short-term oral ethanol administration.

The disposition of ethanol and its metabolite, acetaldehyde, and the activity of alcohol dehydrogenase (ADH) and aldehyde dehydrogenases (ALDH) were determined in the third-trimester pregnant guinea pig following single and 7-day oral administration of ethanol (0.5 g X kg maternal body weight-1 X day-1). Animals were killed at each of selected times after the single and seventh ethanol dose. For both ethanol dosage regimens, the maternal and fetal blood and brain ethanol concentrations were virtually identical during the elimination phase of the time-course study. There was initial slow transfer of ethanol into amniotic fluid, followed by significantly higher ethanol concentration in amniotic fluid relative to maternal and fetal blood during the elimination phase. Acetaldehyde was measurable in maternal blood, maternal brain, and fetal brain at concentrations that were low and variable. For both ethanol dosage regimens, ADH activity was measurable only in maternal liver. Low Km ALDH activity was measurable only in maternal liver and fetal liver. High Km ALDH was measurable in maternal liver, fetal liver, and placenta and was significantly greater in maternal liver. The data indicate that there is bidirectional placental transfer of ethanol in the maternal-fetal unit; the elimination of ethanol from the maternal and fetal compartments is regulated by maternal hepatic biotransformation involving ADH; the amniotic fluid is a reservoir for ethanol in utero; the low Km ALDH in fetal liver protects the fetus from ethanol-derived acetaldehyde in the maternal circulation; and short-term maternal administration of once-daily, low-dose ethanol does not produce major changes in ethanol disposition and the activity of the enzymes involved in ethanol biotransformation.

Alcohol Oxidoreductases↗
PubMed1986

Endothelium-dependent relaxation of rabbit aorta by acetylcholine requires ethylenediaminetetraacetic acid.

Experiments were conducted to determine if ethylenediaminetetraacetic acid (EDTA) was essential for the acetylcholine (ACh)-induced relaxation of blood vessels. Isolated rabbit aortic rings were prepared for recording isometric tension. They were maintained in Krebs bicarbonate solution with various concentrations of EDTA. With EDTA concentrations of 0 or 0.003 mM, no ACh-induced relaxation was observed; only the contractile effect of ACh was seen. With 0.03 and 0.30 mM EDTA, ACh induced relaxation with EC50 values of 0.11 and 0.098 microM, respectively. Under the experimental conditions used, EDTA was essential for demonstration of ACh-induced relaxation.

Acetylcholine↗
PubMed1986

Pharmacokinetics of ethanol and its metabolite, acetaldehyde, and fetolethality in the third-trimester pregnant guinea pig for oral administration of acute, multiple-dose ethanol.

The pharmacokinetics of ethanol and its metabolite, acetaldehyde, were determined in the third-trimester pregnant guinea pig (56-59 days gestation) for oral intubation of four doses of 1 g ethanol/kg maternal body weight, administered at 1-h intervals. Animals (n = 4-7) were sacrificed at each of selected times during the 26-h study. Ethanol and acetaldehyde concentrations were determined by headspace gas-liquid chromatography. The maternal and fetal blood ethanol concentration-time curves were virtually superimposable, which indicated unimpeded bidirectional placental transfer of ethanol in the maternal-fetal unit. The blood and brain ethanol concentrations were similar in each of the maternal and fetal compartments during the study, which indicated rapid equilibrium distribution of ethanol. There was accumulation of ethanol in the amniotic fluid resulting in higher ethanol concentration compared with maternal and fetal blood during the elimination phase, which indicated that the amniotic fluid may serve as a reservoir for ethanol in utero. Acetaldehyde was measurable in all the biological fluids and tissues at concentrations that were at least 1,000-fold less than the respective ethanol concentrations and were variable. There was ethanol-induced fetolethality that was delayed and variable among animals, and was 55% at 23 h. At this time interval, the ethanol concentrations in maternal blood and brain, fetal brain, and amniotic fluid were 35- to 53-fold greater and the acetaldehyde concentrations in maternal blood and fetal brain were four- to five-fold higher in the animals with dead fetuses compared with the guinea pigs with live litters. These data indicated that decreased ethanol elimination from the maternal-fetal unit was related temporally to the fetolethality.

Acetaldehyde↗
PubMed1986

Biotransformation of glyceryl trinitrate occurs concurrently with relaxation of rabbit aorta.

This study was conducted to test the hypothesis that biotransformation of glyceryl trinitrate (GTN) is involved in GTN-induced relaxation of vascular smooth muscle. Isolated rabbit aortic strips (RAS) were contracted submaximally with phenylephrine (PE) and then were incubated with 0.5 microM [14C]GTN in a time course study. GTN-induced relaxation (inhibition of PE-induced tone) of RAS was monitored and tissue GTN and glyceryl-1,2- and 1,3-dinitrate (GDN) concentrations were measured by thin-layer chromatography and liquid scintillation spectrometry at 0.5, 1, 2 and 20 min after incubation. Biotransformation of GTN to GDN occurred during GTN-induced relaxation of RAS. The tissue GDN concentration was dependent on the time duration of incubation with GTN and was related to the magnitude of GTN-induced tissue relaxation. At the 20-min interval, the GDN concentration in the incubation medium indicated appreciable efflux of GDN metabolites from the RAS. In the biotransformation of GTN by RAS, there was about 4-fold preferential formation of 1,2-GDN compared with 1,3-GDN. RAS were made tolerant to GTN in vitro by incubation with 500 microM GTN for 1 hr. After washing, GTN-tolerant and nontolerant (incubation with vehicle for 1 hr) RAS were contracted submaximally with PE, and then were incubated with 0.5 microM [14C]GTN for 2 min. GTN-induced relaxation of RAS and tissue GDN concentration were significantly less for GTN-tolerant tissue compared with nontolerant tissue. Tissue GTN concentration was similar for both GTN-tolerant and nontolerant RAS, which indicated that the tissue uptake of GTN was similar and that GTN biotransformation was diminished in tolerant tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Requirement for reduced, unliganded hemoprotein for the hemoglobin- and myoglobin-mediated biotransformation of glyceryl trinitrate.

The biotransformation of glyceryl trinitrate (GTN) by hemoglobin (Hb) and myoglobin (Mb) was assessed using solutions of various forms of the hemoproteins, viz., the oxy-, deoxy-, carbonmonoxy- and met-forms. After incubation with these, GTN loss was observed only with the deoxy-forms of Hb and Mb. The stoichiometry and products of [14C]GTN biotransformation by deoxy-Hb and deoxy-Mb were determined by measuring the formation of [14C]glyceryl dinitrate [14C]GDN), met-Hb (or met-Mb) and inorganic nitrite anion. Biotransformation of GTN involved the oxidation of 2 mol of heme iron (II) per mol of GTN biotransformed to GDN and inorganic nitrite anion. In addition to the formation of GDN, 1 to 2.5% of the radioactivity could not be extracted from the incubation samples. The ratio of 1,2-GDN/1,3-GDN formed during incubation of deoxy-Hb with GTN was 11:1, which indicated a high degree of regioselectivity for the denitration of the nitrate ester group in position 1 or position 3 of GTN. The metabolite ratio obtained for deoxy-Mb incubation with GTN (1,2-GDN/1,3-GDN,3:1) was less than that for deoxy-Hb, which indicated less regioselectivity for the deoxy-Mb-mediated denitration reaction. This could reflect differences in the topography of the heme pocket of the two hemoproteins and steric differences in the GTN-hemoprotein interaction.

Biotransformation↗
PubMed1985

Disposition of ethanol in maternal blood, fetal blood, and amniotic fluid of third-trimester pregnant ewes.

The disposition of ethanol in maternal arterial blood, fetal arterial blood, and amniotic fluid of nine conscious, cannulated pregnant ewes (128 to 137 days' gestation) was determined for 1-hour maternal intravenous infusion of ethanol, 1 gm/kg maternal body weight. The maternal arterial blood and fetal arterial blood ethanol concentration-time curves were virtually superimposable up to 14 hours. The apparent zero-order ethanol elimination rates for maternal arterial blood and fetal arterial blood were similar. There was a time lag in the transfer of ethanol into amniotic fluid relative to fetal arterial blood, and the peak ethanol concentration in amniotic fluid was significantly lower than the concentrations in maternal arterial blood and fetal arterial blood. The apparent zero-order ethanol elimination rate for amniotic fluid was slower, but not significantly so, compared with the ethanol elimination rates for maternal arterial blood and fetal arterial blood. Ethanol-derived acetaldehyde was found in maternal arterial blood, fetal arterial blood, and amniotic fluid at concentrations at least 1000-fold lower than the respective ethanol concentrations. The data indicate that, for administration of this ethanol dosage regimen to the third-trimester pregnant ewe, there is rapid, bidirectional placental transfer of ethanol; elimination of ethanol from the fetus is regulated primarily by maternal elimination of ethanol; the amniotic fluid may serve as a reservoir for ethanol in utero; and there is appreciable acetaldehyde-metabolizing capacity.

Acetaldehyde↗