Biomedical subjects

G M Pacifici

Publications and source records attributed to G M Pacifici.

At least 37 records · Page 2Linked to original sources

PubMed2000

Sulphation of resveratrol, a natural compound present in wine, and its inhibition by natural flavonoids.

1. Resveratrol, a polyphenolic compound present in grape and wine, has beneficial effects against cancer and protective effects on the cardiovascular system. Resveratrol is sulphated, and the hepatic and duodenal sulphation might limit the bioavailability of this compound. The aim of this study was to see whether natural flavonoids present in wine, fruits and vegetables inhibit the sulphation of resveratrol in the human liver and duodenum. 2. In the liver, IC50 for the inhibition of resveratrol sulphation was 12+/-2 pM (quercetin), 1.0+/-0.04 microM (fisetin), 1.4+/-0.1 microM (myricetin), 2.2+/-0.1 microM (kaempferol) and 2.8+/-0.2 microM (apigenin). Similarly, in the duodenum, IC50 was 15+/-2 pM (quercetin), 1.3+/-0.1 microM (apigenin), 1.3+/-0.5 microM (fisetin), 2.3+/-0.1 microM (kaempferol) and 2.5+/-0.3 microM (myricetin). 3. The type of inhibition of quercetin on resveratrol sulphation was studied in three liver samples and was determined to be non-competitive and mixed in nature. Km (mean+/-SD; microM) was 0.23+/-0.07 (control), 0.40+/-0.08 (5 pM quercetin) and 0.56+/-0.09 (10 pM quercetin). Vmax (mean+/-SD; pmol min(-1) x mg(-1)) was 99+/-11 (control), 73+/-15 (5 pM quercetin) and 57 +/- 10 (10 pM quercetin). Kj and Kies estimates (mean+/-SD) were 3.7+/-1.8 pM and 12.1+/-1.7 pM respectively (p = 0.010). 4. Chrysin was a substrate for the sulphotransferase(s) and an assay was developed for measuring the chrysin sulphation rate in human liver. The enzyme followed Michaelis-Menten kinetics and Km and Vmax (mean+/-SD) measured in four livers were 0.29+/-0.07 microM and 43.1+/-1.9 pmol x min(-1) x mg(-1) respectively. 5. Catechin was neither an inhibitor of resveratrol sulphation nor a substrate of sulphotransferase. 6. These results are consistent with the view that many, but not all, flavonoids inhibit the hepatic and duodenal sulphation of resveratrol, and such inhibition might improve the bioavailability of this compound.

Aged↗

PubMed1999

Interethnic and interindividual variabilities of platelet sulfotransferases activity in Italians and Finns.

OBJECTIVE: The aim of this investigation was to see whether there was interethnic variability in the platelet activities of catechol- and phenol sulfotransferases in Italians and Finns. METHODS: The activities of catechol- and phenol sulfotransferases were measured in platelets obtained from 103 Italian and 74 Finnish individuals. Blood donors were obtained from healthy volunteers free from drugs and without apparent disease. The activities of catechol- and phenol sulfotransferases were measured with 60 microM dopamine and 4 microM 4-nitrophenol as substrates, respectively. RESULTS: The activity of catechol sulfotransferase was not gender dependent and the median estimates (pmol/min/mg) were 9.10 in Italians and 6.37 in Finns (P = 0.0018). The activity of phenol sulfotransferase activity was gender dependent in Finns but not in Italians. The median estimates (pmol/min/mg) were 3.81 in Finnish men and 1.18 in Finnish women (P = 0.0007). In Italian men and women, the median estimates (pmol/min/mg) of phenol sulfotransferase activity were 1.25 and 1.24, respectively (NS). CONCLUSION: This study shows that platelet catechol sulfotransferase activity is greater in Italians than Finns and that the activity of phenol sulfotransferase is gender regulated in Finns but not in Italians. Thus, interethnic differences exist in platelet sulfotransferases between Italians and Finns.

Adult↗

PubMed1998

Catechol-O-methyltransferase: variation in enzyme activity and inhibition by entacapone and tolcapone.

OBJECTIVE: The aim of this investigation was to study the variation of catechol-O-methyltransferase (COMT) activity in the human liver, duodenal mucosa and renal cortex, and to investigate the inhibition of COMT by entacapone and tolcapone. This study included 87 samples of human liver, 94 samples of the duodenum and 72 samples of the renal cortex. RESULTS: The activity of COMT was measured with 3,4-dihydroxybenzoic acid (242 micromol x l(-1)), the methyl acceptor substrate, and adenosyl-L-methionine (44 micromol x l(-1)), the methyl donor substrate. The hepatic activity of COMT activity was significantly higher in men than in women, whereas it was not sex-dependent in the duodenum or renal cortex. The activity of COMT varied 4.4-fold in the liver of men, 2.6-fold in the duodenum and 5.3-fold in the renal cortex. The median estimates of COMT activity were 577, 499, 103 and 159 pmol x min(-1) x mg(-1) in the liver of men and women, in the duodenum and in the renal cortex, respectively. CONCLUSION: Entacapone and tolcapone were powerful inhibitors of COMT and their IC50 estimates were 151 and 773 nM (P = 0.008), respectively, in the liver; consistent results were obtained with the other tissues.

Adult↗

PubMed1998

Interindividual variability of histamine N-methyltransferase in the human liver and kidney.

1. The aim was to investigate the possibility of interindividual variability of histamine N-methyltransferase (HNMT) in the human liver and renal cortex. The activity of HNMT was measured in 99 specimens of the human liver and in 75 specimens of the renal cortex. 2. In the liver the activity of HNMT was positively skewed. It ranged 2.9-fold with a median of 1.72 pmol/min/mg. In the renal cortex the activity of HNMT was normally distributed and ranged 2.6-fold with a mean and coefficient of variation of 1.35 pmol/min/mg and 21%, respectively. 3. The activities of catechol methyltransferase and thiopurine methyltransferase were measured in the renal cortex and any correlations with HNMT activity were assessed. There was a weak but significant correlation (r = 0.294, p = 0.010) between HNMT and catechol methyltransferase activities whereas HNMT activity was not correlated with thiopurine methyltransferase activity. 4. These results are consistent with the view that HNMT is well expressed in the human liver and renal cortex and that it varies among subjects.

Catechol O-Methyltransferase↗

PubMed1997

Sulphation of the heterocyclic amine 1,2,3,4-tetrahydroisoquinoline in the human liver and intestinal mucosa: interindividual variability.

The sulphation rate of 1,2,3,4-tetrahydroisoquinoline (TIQ) was measured in the human liver and in the intestinal mucosa isolated from the transverse colon, ileum and duodenum. The rate (mean +/- SD) of hepatic TIQ sulphation was 500 +/- 174 pmol/min per mg in women (n = 61) and 591 +/- 201 in men (n = 39; P = 0.0087), varying over one order of magnitude in men and women. The sulphation rate of testosterone showed the same sex-dependent pattern and was correlated (r = 0.6055; P < 0.001) with that of TIQ. The frequency distribution of TIQ sulphation rate in human liver was bimodal: 70% of the population fell into the low-activity subgroup and the remaining 30% feel into the high-activity subgroup. In the colon (n = 56), the rate of TIQ sulphation was 30.4 +/- 15.6 pmol/min per mg and the values were similar in men and women (29.8 and 30.9 pmol/min per mg, respectively) but, varied over one order of magnitude and correlated (r = 0.7231; P < 0.001) with that of 4-nitrophenol. The rate of TIQ sulphation changed along the human bowel and mean (+/-SD) estimates for duodenum, ileum and transverse colon were 444 +/- 25, 182 +/- 87 and 30.4 +/- 15.6 pmol/ min per mg, respectively. The present results are consistent with the view that the heterocyclic amine TIQ is sulphated in the human liver and intestinal mucosa. TIQ-sulphotransferase activity varies among subjects and is mostly associated with the liver and duodenum.

Adult↗

PubMed1997

(-)-salbutamol sulphation in the human liver and duodenal mucosa: interindividual variability.

1. Salbutamol as a beta 2-adrenergic agonist used in the treatment of lung obstructive disease and premature labour. It has a bioavailability of 50% and sulphation is the main route of its metabolism. (-)-Salbutamol retains most of the beta 2-adrenergic activity and, thereby, we describe the interindividual variability in the sulphation rate of (-)-salbutamol in 100 specimens of human liver and duodenal mucosa. 2. The mean rate (pmol/min/mg of salbutamol sulphation was 498 in the duodenum and 141 in the liver with 4-fold variation within +/-2 SD units in both tissues. 3. A modelling approach based on the comparison of the best fittings obtained using a gaussian and the sum of two gaussian curves revealed the presence of two subgroups in the hepatic rate of salbutamol sulphation and their means were 69.5 and 105 pmol/min/mg (p < 0.05). In the duodenum, the rate of salbutamol sulphation approached normality. 4. The rates of salbutamol and 4-nitrophenol sulphation correlated highly (r = 0.853; p < 0.001) in the liver whereas in duodenum the rates of salbutamol and dopamine correlated highly (r = 0.914; p < 0.001), 4-Nitrophenol and dopamine are the diagnostic substrates of phenol- and catechol-sulphotransferases respectively. These findings are consistent with the view that the rate of salbutamol sulphation is higher in the gut than in liver and it varies considerably in both tissues.

Adrenergic beta-Agonists↗

PubMed1996

Interindividual variability in the rate of salbutamol sulphation in the human lung.

The beta2-adrenergic agonist salbutamol is administered by inhalation to treat lung-obstructive disease. Salbutamol is metabolized by conjugation with sulphate, and the sulphation of salbutamol was investigated in human lung. Specimens of lung were obtained at lobectomy from 11 non-smokers, 39 smokers and 46 ex-smokers, the latter refraining from smoking at least 6 months before surgery. Neither sex nor ageing influenced the activity of sulphotransferase. The rate of salbutamol sulphation (pmol center dot min-1 center dot mg-1) was greater in non-smokers (27.7) than in smokers (21.3), whereas it was similar in smoker and ex-smokers (22.8). The rate of salbutamol sulphation ranged up to six fold and its distribution did not deviate from normality. As the rate of formation of the inactive salbutamol sulphate varied in the lung, the availability of salbutamol and, in turn, the evoked pharmacological effect should vary in parallel. The activities of salbutamol and dopamine sulphotransferase correlated, suggesting that catechol sulphotransferase takes part in the sulphation of salbutamol. The sulphation of salbutamol is stereoselective in the human lung, the kM estimate for (+)- salbutamol (1198 mu M) being greater than those for either (-)-salbutamol (190 mu M) and racemic salbutamol (142 mu M). These results are consistent with the view that (-)-salbutamol is a better substrate than (+)-salbutamol for sulphotransferase.

Adrenergic beta-Agonists↗

PubMed1996

Variability in the rate of 6-mercaptopurine methylation in the erythrocytes, liver and kidney in an Italian population.

OBJECTIVE: The polymorphism of erythrocyte thiopurine methyltransferase (TPMT) is genetically regulated as an autosomal codominant trait, and so should be congenital. RESULTS: We tested this hypothesis by measuring TPMT activity in erythrocyte preparations from adults and newborns and observed polymorphic distribution of TPMT activity in the adult and newborn erythrocytes. The activity of TPMT was higher in red cells from the newborns than adults. The frequency distribution of TPMT activity was also investigated in the liver and kidney. In the kidney, TPMT activity fell into two subgroups, whereas in the liver the distribution pattern was more complex. The activity of TPMT in erythrocytes and liver from the same subject was correlated, but the values of only half the cases fell within the 95% confidence limits, suggesting that the control of hepatic and/or erythrocyte TPMT is multifactorial.

Adolescent↗

PubMed1996

Captopril methylation in human liver and kidney: interindividual variability.

1. The methylation of captopril was studied in the microsomal fraction obtained from 87 specimens of human liver and 70 specimens of human renal cortex. 2. The rate captopril methylation ranged over one order of magnitude in the liver and kidney. In the human liver, the mean (+/- SD) rate of captopril methylation (pmol/min/mg) was significantly (p < 0.001) greater in women (199 +/- 97) than in men (126 +/- 88), whereas in the kidney no sex-difference was observed, and the mean (+/- SD) of all cases was 47 +/- 23 pmol/min/mg. 3. In the kidney, the statistical analysis revealed the presence of two subgroups in the rate of captopril methylation and their mean (+/- SD) estimates were 42.5 +/- 13.9 and 90.3 +/- 12.0 pmol/min/mg (p < 0.05). Of the population, 84% fell in the former and the remaining 16% in the latter subgroup. 4. Captopril is mainly eliminated by metabolism and its bioavailability is 65%. Methylation is one of the metabolic routes of captopril and its variability may contribute, to some extent, to modulate the intracellular concentration of this drug.

Adult↗

PubMed1996

Zidovudine glucuronidation in human liver: interindividual variability.

Zidovudine 3'-azido-3'-deoxythymidine is the drug chosen for the treatment of patients suffering from AIDS; zidovudine being a potent inhibitor of HIV replication. The drug is extensively metabolized by conjugation with glucuronic acid into an inactive compound, and 30-40% of the dose is eliminated presystemically. We studied the variability and characterized the frequency distribution of the activity of zidovudine glucuronosyl transferase in 93 specimens of human liver. A rapid and reproducible radiometric assay for the glucuronidation of 14C-zidovudine is reported. The method is based on the extraction of the unreacted zidovudine into organic solvents and the radioactivity of the unextractable zidovudine glucuronide was measured in the aqueous phase residue. The rate of zidovudine glucuronidation was neither sex- nor age-dependent, ranged over 1 order of magnitude, and was positively skewed. The possibility that endogenous bilirubin should interact with glucuronidation of zidovudine was explored and the endogenous concentration of bilirubin was measured in the microsomal preparations of 59 liver samples. The final concentration of bilirubin in the assay mixture for zidovudine glucuronidation ranged between 2.2 and 13.2 microM and did not interact with the rate of zidovudine glucuronidation. The kinetics of glucuronosyl transferase towards zidovudine was studied in 20 livers, Michaelis-Menten kinetics were observed and the K(m) estimate ranged over 2-fold with an average of 2.89 mM. These in vitro results are consistent with the view that the rate of glucuronidation varies over 1 order of magnitude in the human liver and its distribution is positively skewed. This variability may modulate the patient's exposition to zidovudine and thereby the efficacy of therapy.

Adult↗

PubMed1995

Placental transfer of drugs administered to the mother.

Drugs administered to mothers have the potential to cross the placenta and reach the fetus. Under particular circumstances, the comparison of the drug concentration in the maternal and fetal plasma may give an idea of the exposure of the fetus to the maternally administered drugs. In this review drugs are classified according to their type of transfer across the placenta. Several drugs rapidly cross the placenta and pharmacologically significant concentrations equilibrate in maternal and fetal plasma. Their transfer is termed 'complete'. Other drugs cross the placenta incompletely, and their concentrations are lower in the fetal than in maternal plasma. The majority of drugs fit into 1 of these 2 groups. A limited number of drugs reach greater concentrations in fetal than maternal plasma. It is said that these drugs have an 'exceeding' transfer. The impression prevails that suxamethonium chloride (succinylcholine chloride) and doxorubicin do not cross the placenta. However, a careful analysis of the literature suggests that this impression is wrong and that all drugs cross the placenta, although the extent transfer varies considerably. The following parameters were considered as possible factors determining the extent of placental transfer: (i) the molecular weight of the drug; (ii) the pKa (pH at which the drug is 50% ionised); and (iii) the extent of drug binding to the plasma protein. Drugs with molecular weights greater than 500D have an incomplete transfer across the human placenta. Strongly dissociated acid drug molecules should have an incomplete transfer, but this does not seem to be an absolute rule. For example, ampicillin and methicillin transfer completely and they are strongly dissociated at physiological pH. The extent of drug binding to plasma protein does not influence the type of drug transfer across the human placenta.

Anesthetics↗

PubMed1995

Glutathione conjugation with 1-chloro-2,4-dinitrobenzene (CDNB): interindividual variability in human liver, lung, kidney and intestine.

The rate of glutathione conjugation with 1-chloro-2,4-dinitrobenzene (CDNB) was measured in specimens of human liver (n = 93), sigmoid colon (n = 56), renal cortex (n = 67) and lung (n = 68). In the liver there was a weak but significant (r = - 0.247 p = 0.017) negative correlation between the activity of glutathione transferase and the liver donor's age. Such a correlation was not found in the renal cortex, lung and colon. In the renal cortex and in lung the rate of glutathione conjugation with CDNB was a little but significantly (p < 0.05) higher in women than men, whereas no sex-dependent difference was observed in the liver and colon. The distribution of glutathione transferase activity was polymorphic in the mucosa of colon and renal cortex of men but not in that of women. Smoking seems not to affect the glutathione conjugation rate with CDNB in lung. The activity of glutathione transferase was 2-, 6-, and 7-fold greater in liver than in the renal cortex, lung and colon, respectively. There was a large interindividual variability of the hepatic glutathione transferase activity, and because this variability, 15% of the population studied catalyzed the glutathione conjugation with CDNB at a rate similar to those of the renal cortex and duodenum. The subjects with low expression of the hepatic glutathione transferase should be more exposed to the effects of toxic and carcinogenic compounds.

Adult↗

PubMed1994

Stereoselective inhibition by chloroquine of histamine N-methyltransferase in the human liver and brain.

This study was designed to determine whether both enantiomers of chloroquine inhibit histamine N-methyltransferase. The mean estimates of IC50 for the d- and l-enantiomers of chloroquine were 4.9 and 17.8 microM (liver), respectively and 6.9 and 21.6 microM (brain), respectively. Ki estimates were significantly lower with d- than with l-chloroquine; hence, d-chloroquine interacts with the enzyme more effectively than l-chloroquine. If the adverse effects of chloroquine are due to the inhibition of histamine N-methyltransferase, therapy with the l-enantiomer might have lower toxicity. The residual activity of histamine N-methyltransferase should reflect both the degree of inhibition by chloroquine and the level of enzyme expression. The rate of histamine methylation was measured in 100 human liver samples and its range and fold of variation were 29% and threefold, respectively. Susceptibility to chloroquine should be greater in subjects with limited expression of histamine N-methyltransferase

Adult↗

PubMed1994

Human liver budesonide sulphotransferase is inhibited by testosterone and correlates with by testosterone sulphotransferase.

Budesonide, a corticosteroid used in the treatment of asthma and allergic reactions, is almost entirely cleared by metabolism in man. We describe the sulphation of budesonide in human liver and lung and provide evidences that the sulphation of budesonide is catalysed by testosterone sulphotransferase. A rapid and reproducible radiometric assay for budesonide sulphotransferase is described. Liver specimens were obtained from 35 men and 65 women and lung specimens from 2 women and 17 men. The average hepatic budesonide sulphation rate was significantly higher in men (41.1 pmol.min-1.ml-1) than women (28.2 pmol.min-1.mg-1). In the lung, the mean budesonide sulphation rate was 5.0 pmol.min-1.mg-1. Testosterone strongly inhibited the hepatic sulphation of budesonide, whereas p-nitrophenol and dopamine were poor inhibitors; the IC50 was 7.0 uM (testosterone), 320 uM (p-nitrophenol) and 510 uM (dopamine). The hepatic rates of testosterone, p-nitrophenol and dopamine sulphation were measured in the same samples assayed for budesonide sulphotransferase. There was a correlation between the hepatic rates of budesonide and testosterone sulphation (P < 0.001; r = 0.810). The activity of testosterone sulphotransferase was significantly greater in men than women (22.0 vs. 17.2 pmol.min-1.mg-1), whereas those of dopamine and p-nitrophenol sulphotransferase were not sex dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Interindividual variability of the human hepatic sulphotransferases.

The variability among subjects of the hepatic activities of O-sulphotransferase towards dopamine, p-nitrophenol, testosterone and ethinyloestradiol and of N-sulphotransferase with 1,2,3,4-tetrahydroisoquinoline (TIQ) as substrate is described. The rates of testosterone and TIQ sulphation were higher in men than women whereas those of ethinyloestradiol, dopamine and p-nitrophenol were similar in both sexes. The sulphotransferase activities towards p-nitrophenol and dopamine were positively skewed whereas those towards ethinyloestradiol approached normality. The coefficients of variations for the sulphotransferase activities ranged between 34% and 62% indicating a considerable variability among subjects. The rates of dopamine-, TIQ- and p-nitrophenol-sulphation were measured in the mucosa of the human intestine, and the duodenum/liver ratios were 10, 0.9 and 0.1, respectively. Thus the contribution of the intestine in the sulphation of xenobiotics is substrate dependent.

Adult↗

PubMed1993

Minoxidil sulphation in human liver and platelets. A study of interindividual variability.

Minoxidil requires to be sulphated to exert its hypotensive effect. We report on interindividual variability in the rate of minoxidil sulphation in 118 specimens of human liver and in platelets obtained from 100 healthy subjects and 100 newborns. The frequency distribution histogram of the hepatic activity of minoxidil sulphotransferase was positively skewed; the mean was 631 pmol.min-1 x mg-1. After logarithmic transformation of the enzyme activity, the frequency distribution histogram became symmetrical and did not significantly deviate from normality. The rate of minoxidil sulphation was not different in platelets from adults (0.74 pmol.min-1 x mg-1) and newborns (1.16 pmol.min-1 x mg-1). The frequency distribution histograms were positively skewed and the results of normal equivalent deviation analysis was compatible with the presence of at least two subgroups of sulphotransferase in liver and platelets. Thus, two phenotypes of sulphotransferase exist in human liver and platelets, and the "extensive sulphator" phenotype contributes to skewing the frequency distribution. In platelets, the percentage of subjects that fall in the two subgroups is different at birth and in adulthood. This can explain the different shape of the frequency distribution in newborn and adult platelets and suggests that platelet minoxidil sulphotransferase undergoes modification after birth.

Adult↗

PubMed1993

Sulphation and glucuronidation of ritodrine in human foetal and adult tissues.

Ritodrine is a beta 2-adrenoceptor agonist used for the management of preterm labour. It is inactivated by conjugation with sulphate and glucuronic acid. There is more ritodrine sulphate than ritodrine glucuronide in urine from the newborn whereas equal amounts of ritodrine glucuronide and sulphate are excreted in maternal urine [Clin. Pharmacol. Ther 44, 634-641, 1988]. We show that, in the mid-gestational human fetal liver, ritodrine sulphotransferase is well expressed, whereas the glucuronidation of ritodrine is little developed compared to the adult liver. The average sulphotransferase activity was 308 pmol.min-1 per mg protein in fetal (N = 48) and 145 pmol.min-1 per mg protein in adult (N = 32) liver. The rates of ritodrine sulphation in fetal gut, lung and kidney were higher than in the corresponding adult tissues. The development and tissue distribution patterns of ritodrine sulphotransferase are consistent with those of dopamine sulphotransferase. Ritodrine and dopamine are sulphated by thermolabile enzymes. The activity of glucuronyl transferase was measurable in only 5 of the 48 foetal livers assayed, and in those in which could be assayed, the average activity was 44.6 pmol.min-1 per mg protein, one-tenth of that in adult livers (524 pmol.min-1 per mg protein).

Adult↗

PubMed1993

(+) and (-) terbutaline are sulphated at a higher rate in human intestine than in liver.

The sulphation of (+) and (-) terbutaline was investigated in specimens of human intestinal mucosa isolated from the duodenum, ileum, ascending colon and sigmoid colon and in specimens of liver and lung. The lung specimens came from 8 current smokers and 11 ex-smokers, the latter having stopped at least 3 months before surgery. The rates (pmol.min-1.mg protein-1) of (+) and (-) terbutaline sulphation were 1195 and 948 (duodenum), 415 and 317 (ileum), 268 and 166 (ascending colon), 263 and 193 (sigmoid colon) and 45 and 34 (liver), respectively. Terbutaline sulphotransferase was more active in the small and large intestine than in the liver. In the lung, the rate of (+) terbutaline sulphation was 118 (ex-smokers) and 82 (smokers), and for (-) terbutaline it was 82 (ex-smokers) and 56 (smokers). In the gut, the activity of catechol sulphotransferase was significantly correlated with that of (+)- and (-)- terbutaline sulphotransferase whereas no correlation was found with phenol sulphotransferase. This correlation, the finding of the higher activity of terbutaline sulphotransferase in gut than in liver, and the pronounced thermal inactivation of the enzyme, are all consistent with the view that catechol sulphotransferase has a role in the sulphation of terbutaline.

Adult↗