Analysis of human glutathione S-transferase alpha 1 (hGSTA1) gene promoter polymorphism using denaturing high performance liquid chromatography (DHPLC).

AIM: The GST enzyme, encoded by hGSTA1 gene, catalyses the GSH dependant detoxification of a variety of carcinogenic metabolites and alkylating chemotherapeutic agents. Two genetic variants of hGSTA1, namely hGSTA1*A and hGSTA1*B, are characterized by three linked SNPs, of which -52 G>A variation being solely responsible for the differential promoter activity of hGSTA1. Individuals homozygous for hGSTA1*B have low hepatic expression of hGSTA1. Given the time and labor consuming PCR-RFLP method and the direct prediction of -52 G>A variation, we opted to establish a high throughput DHPLC procedure for the characterization of hGSTA1 variants. METHODS: 117 DNA samples from South India were included in the study. Control samples were generated for DHPLC using conventional PCR-RFLP technique. Heteroduplexes were produced by in vitro mixing of control DNA samples (hGSTA1*A) to all the samples which are subsequently subjected to DHPLC analysis. The samples were analyzed for the presence of heteroduplexes from the chromatographic profiles. RESULTS AND CONCLUSION: From the total of 117 samples, 43.5% are homozygous for hGSTA1*A allele, 13% are homozygous for hGSTA1*B allele and 43.5% are hGSTA1*A/B heterozygotes. This is, to our knowledge, the first report on the use of DHPLC for the evaluation of hGSTA1 gene promoter polymorphism.

Constitutive nitric oxide synthase gene polymorphisms and house dust mite respiratory allergy in an Algerian patient group.

Genetic polymorphisms in neuronal nitric oxide synthase (NOS1) and calmodulin-dependent endothelial NOS (NOS3) genes are known to influence the course of allergic respiratory disorders. We investigated the role of NOS1 -84 G-->A and NOS3 -786 T-->C, 894 G-->T and 27 base pair (bp) repeat polymorphisms in 125 patients suffering from asthma and/or rhinitis and monosensitized against Dermatophagoides pteronyssinus (Dpter) and 111 controls from Algeria. We found a higher frequency of the -786 C NOS3 allele in patients than in controls [corrected P value (Pc) = 0.04], especially in female cases (Pc = 0.02) and that the 'ab' genotype of the 27-bp polymorphism was significantly associated with specific immunoglobulin E production against Dpter (P = 0.006). This study brings further support for the participation of NOS3 gene polymorphism in the pathogenesis of respiratory allergic disorders.

Genotype and allele frequency of CYP2D6 in Tamilian population.

OBJECTIVE: To assess the frequency of CYP2D6 *3, *4, *5 and *10 allelic variants in a South Indian population and compare the frequencies with other major populations. METHODS: Polymerase chain reaction (PCR) or PCR-restriction fragment length polymorphism (RFLP)-based methods were used to identify the CYP2D6 genotypes of 106 healthy unrelated male and female volunteers of Tamilian origin. The allele and genotype frequencies observed were compared with other major populations. RESULTS: The *10 allele was the most frequent mutant allele in Tamilians (20.3%). The *5 allele occurred at 0.9% and the *3 allele was not detected. The most frequent allele causing enzyme inactivation was *4 allele in Tamilians (6.6%), which is significantly higher than that reported in Japanese (0%). CONCLUSIONS: The *10 allele is the most common mutant allele in Tamilians. The CYP2D6*4 and CYP2D6*5 alleles are distributed in a significantly different way in the Tamil population relative to Oriental populations.

Effect of honey on carbamazepine kinetics in rabbits.

The study was undertaken to determine the effect of honey on carbamazepine kinetics in rabbits. The study was done on three occasions in each animal. Study 1 was carried out after single dose administration of carbamazepine (80 mg/kg, po), along with saline (2.34 ml/kg, po). After a wash out period of one week, the second study was carried out by co-administration of carbamazepine with honey (2.34ml/kg, po). After this, the animals continued to receive honey (2.34ml/kg, po), once daily, for 7 days. On the eighth day of honey treatment, the carbamazepine kinetics was studied again. Pharmacokinetic analysis revealed that single as well as multiple dose honey treatment showed a significant decrease in area under the plasma time concentration curve (AUC) when compared with saline treated control. A significant increase in the clearance (CL/F) rate of carbamazepine was observed only after multiple dose honey treatment. Both single and multiple dose honey treatment did not show any significant effect on other pharmacokinetic parameters like t1/2, Cmax, Tmax and Vd when compared with saline treated group. Data thus obtained suggested that honey decreases the bioavailability of carbamazepine.

Influence of honey on orally and intravenously administered diltiazem kinetics in rabbits.

Effect of honey on plasma concentration of diltiazem after oral and intravenous administration in rabbits, has been studied. For oral study, single dose of diltiazem (5 mg/kg, p.o.) along with saline was administered to New Zealand white rabbits (n=8). Blood samples were collected at 0, 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6 and 8 hr after drug administration from marginal ear vein. After a washout period of one week, diltiazem was administered with honey (2.34 ml/kg; p.o.) and the blood samples were collected as above. To the same animals honey (2.34 ml/kg; p.o.) was continued once daily for 7 days. On 8th day, honey and diltiazem were administered simultaneously and blood samples were collected at similar time intervals as mentioned above. For intravenous study the pharmacokinetic was done in each animal on two occasions. The first study was done after single dose administration of diltiazem (5 mg/kg; i.v.) along with saline (2.34 ml/kg; p.o.). Blood samples were collected at 0, 0.083, 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4 and 6 hr after i.v. diltiazem administration. The same animals were treated with honey (2.34 ml/kg; p.o.) for seven days. On day 8, the second study was carried out with single dose i.v. administration of diltiazem along with honey (2.34 ml/kg; p.o.) and blood samples were collected. In the oral study, single dose administration of honey decreased the AUC and Cmax of diltiazem associated with significant increase in clearance and volume of distribution when compared to saline treated group. After one week administration of honey, diltiazem kinetic data showed further reduction in AUC and Cmax and increase in clearance and volume of distribution. In the i.v. study also, multiple dose administration of honey significantly reduced the AUC and increased the clearance value of diltiazem. The results suggest that honey may decrease the plasma concentration of diltiazem after its oral or i.v. administration in rabbits.

Effect of hyperprolactinaemia as induced by pituitary homografts under kidney capsule on gastric and duodenal ulcers in rats.

The effect of hyperprolactinaemia, induced by two or four pituitary homografts under the kidney capsule, on gastric and duodenal ulcers has been studied. The acute gastric ulcer models used were pylorus ligation, indometacin-induced and ethanol-induced gastric ulcers. Chronic gastric ulcers were induced using acetic acid and duodenal ulcers by mercaptamine hydrochloride. After pylorus ligation, there was an approximate 30-40% increase in gastric secretion, a significant increase in total acidity (P < 0.01) and in the ulcer index (P < 0.01) in rats bearing pituitary homografts under the kidney capsule when compared with the sham-operated control. Hyperprolactinaemia did not affect the formation of ethanol-induced gastric ulcers but showed a 40% reduction in the development of indometacin-induced gastric ulcers. It also produced a 20% increase in the ulcer index in acetic acid-induced chronic gastric ulcers and a 30% increase in ulcer area in mercaptamine-induced duodenal ulcers. Our results showed that hyperprolactinaemia induced gastric acid secretion and thereby aggravated gastric and duodenal ulcers in rats. Hyperprolactinaemia did not affect gastric cytoprotection.

Effect of centrally administered oxytocin on gastric and duodenal ulcers in rats.

AIM: To investigate the effect of centrally administered oxytocin and its receptor antagonist, atosiban, on gastric acid secretion and on experimentally induced gastric and duodenal ulcers. METHODS: The acute gastric ulcer models, such as pylorus ligation, indomethacin-induced and ethanol-induced gastric ulcers were used. Chronic gastric ulcers were induced by acetic acid and duodenal ulcers by cysteamine HCl. RESULTS: In pylorus ligated rats, oxytocin (10 microg/kg, icv) showed significant antisecretory and antiulcer activity (P < 0.01). However, it aggravated the ethanol-induced gastric ulcers and did not show any effect on indomethacin-induced gastric ulcers. Oxytocin increased gastric ulcer healing in acetic acid-induced chronic gastric ulcers. The effect of oxytocin was reversed by atosiban (10 microg/kg, icv), a selective oxytocin receptor antagonist. Atosiban when given alone increased gastric acid secretion and ulcer index in pylorus-ligated rats and also aggravated acetic acid-induced chronic gastric ulcers. It seems the antiulcer activity of oxytocin was due to its anti-secretory effect. CONCLUSION: Centrally administered oxytocin possesses gastric anti-secretory and anti-ulcer activity and oxytocin antagonist, atosiban, is pro-ulcerogenic in rats.

Effect of centrally administered prolactin on gastric and duodenal ulcers in rats.

The effect of centrally administered prolactin on gastric acid secretion and experimentally-induced gastric and duodenal ulcers was studied. The acute gastric ulcer models used were pylorus ligation, indomethacin-induced and ethanol-induced gastric ulcers. Chronic gastric ulcers were induced using acetic acid and duodenal ulcers by cysteamine hydrochloride. In pylorus ligated rats, prolactin (1 microg/kg icv) produced 45% increase in gastric content volume, significant increase in free acidity (P < 0.001), total acidity (P < 0.001) and ulcer index (P < 0.001). It did not show any significant effect on ethanol-induced and indomethacin-induced gastric ulcers. Prolactin increased the ulcer index (P < 0.001) and ulcer score (P < 0.05) in acetic acid-induced chronic gastric ulcers. It also increased ulcer area (P < 0.05) in cysteamine-induced duodenal ulcers. Therefore, the proulcerogenic activity of prolactin was due to its gastric hypersecretory effect.

Gastric antisecretory and antiulcer activity of oxytocin in rats and guinea pigs.

The effect of oxytocin (1 mg/kg s.c) on gastric acid secretion and on different experimentally induced gastric and duodenal ulcers was studied. The acute gastric ulcer models used were pylorus ligation, indomethacin, ethanol and histamine induced acute gastric ulcers. Chronic gastric ulcers were induced using acetic acid and duodenal ulcers by cysteamine hydrochloride. Oxytocin showed significant antisecretory and antiulcer activity in pylorus ligated rats. Similarly oxytocin reduced the ulcer index in histamine induced gastric ulcers in guinea pigs and cysteamine induced duodenal ulcers in rats. The antiulcer and antisecretory effect was comparable to that of ranitidine (50mg/kg, i.p) though less in intensity. However, it did not show any gastric cytoprotective effect in ethanol and indomethacin induced ulcer models but ranitidine showed protection (p<0.05) in later model. Oxytocin enhanced gastric ulcer healing in acetic acid induced chronic gastric ulcer model. The reversal of oxytocin effect by atosiban, an oxytocin receptor antagonist indicates a role for oxytocin receptors. The antiulcer activity of oxytocin can be attributed to its antisecretory effect.

Effect of two types of Indian breakfast on bioavailability of cefuroxime axetil.

BACKGROUND & OBJECTIVES: The oral bioavailability of cefuroxime axetil is enhanced by food. This study was done to compare the effect of two types of Indian breakfast on the bioavailability of cefuroxime axetil in healthy volunteers. METHODS: Eight healthy male volunteers participated in the crossover study. Subjects were randomized to receive either one of the two types of breakfast, Diet-A or Diet-B, 10 min before single dose of 500 mg cefuroxime axetil. After a washout period of one week the study was repeated with the other type of diet. Diet-A included idly with chutney. Diet-B included poori and dal-fry. Blood samples for pharmacokinetic analysis were obtained prior to dosing and at 0.25, 0.50, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0 and 8.0 h following dosing and urine collections were done for 8 h. The serum and urine samples were assayed by using HPLC. RESULTS: The AUC and Cmax were significantly increased after oral administration of cefuroxime axetil with Diet-B, when compared to Diet-A (P < 0.01 and P < 0.02 respectively). The values of apparent absorption rate constant, lag-time, Tmax and t1/2 beta for the two regimens were not significantly different. The volume of distribution and plasma clearance for cefuroxime were significantly lower (P < 0.02, P < 0.001 respectively) in the regimen with Diet-B. The 8 h urinary recovery of cefuroxime was 16.59 and 28.44 per cent (P < 0.005) with Diet-A and Diet-B respectively. INTERPRETATION & CONCLUSIONS: The administration of cefuroxime axetil with poori and dal-fry may enhance the bioavailability when compared with idly and chutney.

Genetic polymorphism of CYP2D6 in Karnataka and Andhra Pradesh population in India.

AIM: To study the prevalence of cytochrome P-450 2D6 (CYP2D6) polymorphism in Karnataka (KA) and Andhra Pradesh (AP) population. METHODS: Two hundred and eleven healthy human volunteers participated in the study (100 from KA and 111 from AP). At bed time, after voiding their bladder, the volunteers ingested 30 mg of dextromethorphan hydrobromide (DM). Urine samples were collected for 8 h. DM and its metabolite dextrorphan (DT) were estimated in the urine using HPLC. The metabolic ratio (DM/DT) was used for phenotyping. RESULTS: The prevalence of poor metabolisers (PM) in KA is 4% and AP is 1.8%. CONCLUSION: The frequency of PM phenotype in South Indian population is in between the Western and Oriental population.