Human genome project: pharmacogenomics and drug development.

Now that all 30,000 or so genes that make up the human genome have been deciphered, pharmaceutical industries are emerging to capitalize the custom based drug treatment. Understanding human genetic variation promises to have a great impact on our ability to uncover the cause of individual variation in response to therapeutics. The study of association between genetics and drug response is called pharmacogenomics. The potential implication of genomics and pharmacogenomics in clinical research and clinical medicine is that disease could be treated according to the interindividual differences in drug disposition and effects, thereby enhancing the drug discovery and providing a stronger scientific basis of each patient's genetic constitution. Sequence information derived from the genomes of many individuals is leading to the rapid discovery of single nucleotide polymorphisms or SNPs. Detection of these human polymorphisms will fuel the discipline of pharmacogenomics by developing more personalized drug therapies. A greater understanding of the way in which individuals with a particular genotype respond to a drug allows manufacturers to identify population subgroups that will benefit most from a particular drug. The increasing emphasis on pharmacogenomics is likely to raise ethical and legal questions regarding, among other things, the design of research studies, the construction of clinical trials and the pricing of drugs.

Effect of flavone in a canine model of myocardial stunning.

Putative cardioprotective action of flavone (10, 20 and 30 mg/kg) was investigated in a canine model of regional ischemia (20 min) followed by 60 min of reperfusion. In animals pretreated with vehicle, myocardial stunning was evidenced by significant changes in hemodynamic parameters (depressed mean arterial pressure, LV peak (+) dP/dt, LV peak (-) dP/dt and elevated LV end-diastolic pressure) and biochemical parameters (decreased myocardial ATP and rise in plasma malondialdehyde or MDA; a marker of free radical-induced injury). A reduction in plasma MDA was noted with 20 and 30 mg/kg flavone, although attenuation of myocardial dysfunction was evident with all the three doses. The results suggest that besides a significant dose-dependent antioxidant effect, flavone may also have some cardioprotective actions per se, which needs to be further investigated.

Role of nutrition in toxic injury.

The importance of nutrition in protecting the living organism against the potentially lethal effects of reactive oxygen species and toxic environmental chemicals has recently been realized. This new perspective has prompted re-evaluation of the food constituents of human diet from the point of view of their nutritional adequacy, deficiency and toxicity. The biological antioxidant defense system is an integrated array of enzymes, antioxidants and free radical scavengers. These include glutathione reductase, glutathione-s-transferase, glutathione peroxidase, phospholipid hydroperoxide glutathione peroxidase, superoxide dismutase (SOD) and catalase, together with the antioxidant vitamins C, E and A. The individual components of this system get utilized in various physiological process and for chemoprotection and therefore require replenishment from the diet. Other components of the diet like carbohydrates, proteins and lipids are important for maintaining the levels of various enzymes required in body's defense system providing protection against carcinogens. However, the emerging newer concepts focus on the role of trace elements and other dietary components in antioxidant defense and detoxification mechanisms. Trace elements like Iron, zinc magnesium, selenium, copper, and manganese are some of the elements involved in antioxidant defense mechanisms. Inadequate intake of these nutrients has been associated with ischemic heart disease, arthritis, stroke and cancer, where pathogenic role of free radicals is suggested. Further the importance of diet in the prevention of chemical induced toxicity can not be undetermined. Recent reports on the role of bioflavonoids as antioxidents and their potential use to reduce the risks of coronary heart disease and cancer in human beings have opened a new arena for future research. Induction of the cytochrome P450 isoenzymes by food pyrolysis, mutagens, alcohol and fasting, on the other hand is reported to contribute to chemical toxicity and carcinogenecity. Certain chemicals moieties in the food are mutagenic and carcinogenic.

Role of Lipistat in protection against isoproterenol induced myocardial necrosis in rats: a biochemical and histopathological study.

A test drug (Lipistat) comprising of equal-proportions of extracts of Terminalia arjuna, Inula racemosa Hook, latex of Commiphora mukul, in three different doses (225 mg/kg; 350 mg/kg; 450 mg/kg) were administered orally daily for 6 days a week for 60 days in rats. Thereafter, the rats were subjected to isoproterenol (ISO) induced (85 mg/kg, s.c. for 2 days) myocardial necrosis. Gross and microscopic examinations (histopathology) were done along with estimations of myocardial tissue high energy phosphates (HEP) stores and lactate content. Gross examination showed significant (P < 0.05) cardioprotection in Lipistat treated animals. On microscopic examination no statistically significant reduction in myocardial damage by 350 and 450 mg/kg of Lipistat were observed although loss of myocardial HEP stores and accumulation of lactate were significantly prevented. The results of the present study suggest the potential usefulness of Lipistat in the prevention of ischemic heart disease.

Oxyfedrine in myocardial stunning.

Effect of oxyfedrine (OXF)(1 mg/kg) administered just before reperfusion (post-treatment) was investigated in a canine model of myocardial stunning. In the saline-treated animals, myocardial stunning was evidenced by fall in MAP, decrease in LV peak (+) dP/dt, rise in LVEDP and incomplete regeneration of myocardial ATP, after reperfusion. OXF was found to be effective in preventing the haemodynamic and metabolic changes associated with myocardial stunning.

An experimental study on cardiotoxicity of aluminium phosphide.

Aluminium phosphide(AlP), a grain fumigant pesticide, was studied for its cardiotoxicity in anaesthetised rats. The hemodynamic and cardiac biochemical changes were investigated following intragastric administration of different doses of AlP (10, 20 and 40 mg). With 10 and 20 mg dose of AlP an immediate fall in BP was observed which recovered partially and stabilized for 10 minutes followed by a gradual fall till the animal died. However, with a higher dose (40 mg) there was no recovery in BP, instead the initial fall continued till the death of the animal. An increase in the heart rate was observed with 10 and 20 mg dose of AlP for 15 minutes which was followed by a marked fall till cardiac arrest ensued. On the other hand, 40 mg dose produced only a transient tachycardia followed by a prolonged bradycardia. ECG changes at all dose levels included initial tachycardia and ST segment elevation progressing to QRS broadening. However, marked conduction defects as evidenced by the ventricular ectopics were noticed only with 40 mg. The mean survival time dose dependently decreased with 10 mg(55 +/- 3 min), 20 mg(35 +/- 2 min) and 40 mg(18 +/- 2 min) of AlP. The cardiac glycogen, ATP and CP levels were significantly lowered in animals treated with 10, 20 and 40 mg of AlP. Higher levels of MDA in the cardiac tissue were observed with 10, 20 and 40 mg of AlP. Thus it is suggested that the deleterious effect of AlP on heart is mediated by both declined cellular metabolism of the myocardium as well as by necrosis of the cardiac tissue resulting in the release of reactive oxygen intermediates.

Effect of short and long-term exposure to diesel exhaust on sensitivity of guinea pig tracheal preparation to histamine.

Single exposure, to diesel exhaust (1 part exhaust diluted by 5 parts of clean air) reduced EC50 of histamine indicating hyperresponsiveness of the receptors in trachea of exposed guinea pigs. In contrast, following repeated exposure for 7, 14 or 21 days (15 min/day), EC50 was progressively increased indicating the possibility of down-regulated histamine receptors. Further, simultaneous significant increase in histamine levels (bioassayed on guinea pig ileum) in bronchial airway lavage fluid supports the aforementioned hypothesis. The change in lung/body weight ratio and suspended particulate matter deposited on filters followed the same temporal pattern as EC50. The findings are suggestive of differential effects of diesel exhaust on airway depending upon the duration of exposure.

Involvement of renin-angiotensin system in hypertensive effect of cadmium in rats.

Role of renin-angiotensin system in hypertension induced by cadmium chloride (CdCl2) in rats has been investigated. Intravenous administration of CdCl (1 mg/kg) produced a biphasic response i.e. a transient fall followed by a marked and consistent rise in blood pressure. The peak hypertensive effect was accompanied by raised PRA levels. Pretreatment with captopril (1 mg/kg, i.v.) losartan (1 mg/kg, i.v.) or captopril + losartan attenuated the pressor response to Cd by 62%, 42% and 100% respectively in separate groups. Central administration of Cd (10 micrograms/rat, i.c.v.) showed a biphasic response similar to that observed after i.v. route. However, it was not accompanied by raised PRA levels. Prior treatment with losartan (10 micrograms/rat, i.c.v.) completely abolished the pressor response to Cd (i.c.v.) whereas it was not affected significantly by captopril (10 micrograms/rat, i.c.v.). On the other hand, centrally administered losartan only partially reduced the pressor response to i.v. Cd. The results are discussed in light of a differential involvement of central vs peripheral renin-angiotensin system in the hypertensive effect of Cd.

Cadmium induced nephrotoxicity in rats.

Onset of hypertension and nephropathy after 1,2, and 4 weeks of exposure to cadmium chloride (1 mg/kg, ip) was studied in rats by measuring changes in blood pressure and renal function (urinary output, electrolytes, serum creatinine, inulin clearance and Na+K+ ATPase). Significant decrease in body weight and rise in blood pressure were observed as early as one week of exposure while microalbuminuria was detected in 50% of the animals after 2 weeks. Na+K+ ATPase, a renal tubular enzyme, was depressed after 1 week with maximum lowering occurring after 4 weeks. There were no detectable changes in fluid intake, urine output, electrolytes, inulin clearance and serum creatinine even after 4 weeks. It is concluded that hypertension and tubular lesion set in earlier than glomerulopathy as indicated by microalbuminuria and the latter could be the consequence of rise in blood pressure.

Changes in circulatory biogenic amines during head-up tilt testing in neurocardiogenic syncope.

The pathogenesis of neurocardiogenic syncope is not completely understood. To examine the possible role of biogenic amines in patients with neurocardiogenic syncope, 18 consecutive patients (age 30 +/- 13 years, 15 males, 3 females) of unexplained syncope were subjected to Head-Up Tilt Testing (HUTT). Blood was sampled by an indwelling cannula at baseline, end of tilt test (or at syncope) and 1 min after returning to the supine position. Biogenic amines, epinephrine (E), norepinephrine (NE), serotonin (5-HT) and their metabolites, homovanillic acid (HVA) and 5-hydroxy indole acetic acid (5-HIAA), were measured in the serum after serial organic phase extraction by high-performance liquid chromatography (HPLC) using ultraviolet detection at a wavelength of 280 nm. Twelve patients were found to be HUTT negative while 6 patients were HUTT positive. Baseline E, NE and 5-HT levels were significantly greater in the HUTT positive patients [E 510 +/- 154 versus 302 +/- 96 pg/ml (p < 0.01), NE 253 +/- 99 versus 159 +/- 62 pg/ml (p < 0.05), 5-HT 174 +/- 32 versus 118 +/- 22 pg/ml (p < 0.01)]. E and HVA levels at the end of the test were significantly higher in HUTT positive patients [E 788 +/- 268 versus 465 +/- 119 pg/ml (p < 0.01), HVA 308 +/- 91 versus 112 +/- 12 pg/ml (p < 0.001)]. A significantly greater rise of E from the baseline was observed in HUTT positive patients (510 +/- 154 versus 112 +/- 12 pg/ml (p < 0.01)]. The increase in the levels of E and HVA both at baseline and after the tilt test, without a corresponding rise in NE levels indicates enhanced activity of the adrenomedullary axis which is not paralleled by NE release from sympathetic nerve endings in patients of neurocardiogenic syncope.

Gastrointestinal protection by NO from NSAIDs induced injury.

One of the most deleterious side effects of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) is gastric injury. In order to prevent this, attempt has been made to make novel nitric oxide (NO) releasing NSAIDs. The NO-releasing moiety (nitroxybutylester), which is combined with NSAIDs, has been shown to be responsible for gastrointestinal protection. Various NO-releasing NSAIDs have been compared with their parent compounds and marked decrease in gastrointestinal side effects were observed in the former case. Various animal studies have been done in this context. However, exact mechanism of action of NO-releasing NSAIDs is not clear.

Radioimmunoassay of angiotensin-II: methodology and standardization.

The study was planned to set up and standardize the radioimmunoassay of Ang-II and to validate the procedure in terms of precision, sensitivity, specificity and recovery. The application of the developed assay was studied in normal healthy volunteers and in patients of renovascular hypertension (RVHT) and renal hypertension (RH). Synthetic human Ang-II was coupled to BSA by carbodimide condensation to get the hapten carrier conjugate which was injected in rabbits to raise the antibodies. The titre of 1:250 showed significant binding (56.79%) and was used for the assay. The sensitivity of the assay was 2 pg/ml and cross-reactivity with analogues of Ang-II was minimum. Mean Ang-II levels in normal subjects was 16 +/- 3.6 pg/ml. In patients of RVHT and RH, the peripheral blood Ang-II levels were found to be 876 +/- 8.6 and 108 +/- 2.3 pg/ml respectively. In patients of unilateral RVHT, renal vein Ang-II levels of the affected side were significantly higher than the unaffected side (P < 0.001). The results indicate that unextracted samples can be successfully utilized to estimate Ang-II levels.

Comparative bioavailability of two brands of ciprofloxacin.

Twelve adult healthy volunteers participated on two occasions in a cross-over study with an interval of 30 days. The bioavailability of ciprofloxacin 500 mg administered as single oral dose was compared in preparation A (Indian, Torrent) and preparation B (Imported, Bayer). The drug was administered early morning on an empty stomach. Blood samples were collected at 1/2,1,2,4,6,8,12 and 24 hours. Plasma levels of ciprofloxacin were determined by HPLC. Time taken to achieve peak plasma concentration (Tmax) was 2 hours (A) and 1.67 +/- 0.49 hours (B). Maximum plasma concentration (Cmax) ranged from 1.8 to 5.1 ug/ml (mean 3.08 +/- 0.99 ug/ml) for 'A' and 2.08 to 5.5 mu g/ml (mean 3.58 +/- 1.37 mu g/me for 'B'. Area under plasma concentration time curve ranged from 30.91 to 118.27 ug/ml/hr (mean 59.97 +/- 26.68 ug/ml/hr) in 'A' and 36.52 to 108.05 (mean 62.80 +/- 22.33 ug/ml/hr) in 'B' which is more than reported in Western literature. Large bioavailability of ciprofloxacin in the present study suggests the need to be cautious while treating patients with renal problems and to use lower doses in Indian patients to achieve desirable results. However, there was no significant difference in the pharmacokinetic parameters between the two brands (Paired 't' test and Wilcoxon Sign Rank test). It is therefore, concluded that both the preparations are comparable in terms of bioavailability.

Comparative bioavailability of two brands of norfloxacin.

Twelve adult healthy volunteers participated on two occasions in a cross-over study with an interval of 30 days. The bioavailability of norfloxacin 400 mg administered as single oral dose was compared in an Indian preparation A (Torrent) and imported preparation B (Merck Sharp and Dohme (MSD), USA). Plasma was separated from the blood and stored at -20 degrees C for analysis by High Performance Liquid Chromatography. Time taken to achieve mean peak plasma concentration (Tmax) was 2.00 +/- 0.74 hours in case of Torrent (A) and 1.70 +/- 0.49 hours in case of Merck Sharp and Dohme, USA (B). The maximum plasma concentration (Cmax) ranged from 1.60 to 2.87 ug/ml in Torrent (A) and 1.18 to 2.28 ug/ml in case of MSD (B). Area under plasma concentration curve (AUCO-12hr) was 12.70 +/- 3.2 ug/ml/hour for 'A' and 14.80 +/- 2.80 ug/ml/hr for 'B'. Elimination half life (t1/2) for Torrent (A) was 9.25 +/- 5.10 hours and for MSD (B) it was 12.05 +/- 1.05 hours. There was no significant difference in the pharmacokinetic parameters between the two brands (Student's 't' test). Increased elimination half life and large bioavailability (AUC) with both the preparations in the present study suggest the need to be cautious while treating patients with renal problems and to use lower doses in Indian population to achieve desirable kinetics of norfloxacin.

Isoniazid and acetylisoniazid kinetics in serum and urine in pulmonary primary complex with intermittent regimen.

Twenty patients, 1 through 13 years of age from Pediatric Tuberculosis Clinic of All India Institute of Medical Sciences, New Delhi, suffering from pulmonary primary complex (PPC) were investigated for serum and urine concentrations of isoniazid (INH) and acetylisoniazid (AcINH). Patients were put on an intermittent regimen - 2HR, 4H2R2, INH (H) was given in a dose of 10 mg/kg/day for first 2 months (the daily dose phase), followed by 20 mg/kg/dose in biweekly phase of regimen for rest of the 4 months, whereas, rifampicin (R) was given as 12 mg/kg in both daily as well as biweekly phases. In the biweekly phase of regimen, after 7 days of biweekly administration of drugs, INH and AcINH concentrations were estimated by HPLC at 0,1,3,5 and 7 hours in serum, and at 0-3, 3-6, 6-12 and 12-24 hour-intervals of drug administration in urine. Peak concentrations of INH and AcINH (Mean +/- SD) were 2.6 +/- 1.8 and 5.5 +/- 2.6 micrograms/ml in serum (Cmax), and 5.7 +/- 4.8 and 21.5 +/- 12.1 mg in urine, respectively. Time to achieve Cmax (Tmax), for INH and AcINH were 1 and 5 hours respectively while time of peak concentration in urine for INH was 3-6 hours and for AcINH 6-12 hours. The half-life (T1/2) of INH was 4.5 hours and area under serum-concentration time-curve (AUC0-7h) was 20.7 micrograms/ml/h (mean values). In biweekly phase (4H2R2) of regimen, just before administration of next dose, 0 hour (or 72 hours) concentration of INH was estimated at 0.47 +/- 0.3 micrograms/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Recovery from reperfusion injury in intact canine heart by nifedipine.

Effect of nifedipine post-treatment (100 micrograms/kg slow bolus followed by 3 micrograms/kg/min infusion) on the functional and metabolic changes of the heart after a brief regional ischemia (I) (20 min.) followed by 1 hr of reperfusion (R) was studied in pentobarbitone-anaesthetized open-chest coronary ligated dogs. In the control group, 1 hr of reperfusion failed to cause any significant recovery of the depressed LVdP/dtmax and that of the elevated LVEDP (LVdP/dtmax, pre-ischemic: 2720 +/- 90 mm Hg/sec., 20 min. of I: 2410 +/- 120 mm Hg/sec and 60 min. of R: 2210 +/- 130 mm Hg/sec. LVEDP, pre-ischemic: 5.25 +/- 0.2 mm Hg, 20 min. of I: 10.5 +/- 0.9 mm Hg and 60 min. of R: 7.5 +/- 0.5 mm Hg). However, 1 hr of reperfusion caused a significant recovery of ischemia-induced depletion of myocardial creatine phosphate (CP) content only, but not that of ATP. On post-treatment with nifedipine (i.e., infusion started just before reperfusion), there was a significant recovery in LVEDP (8.25 +/- 0.6 mm Hg after 20 min. of ischemia to 5.0 +/- 0.4 mm Hg after 1 hr of reperfusion) and there was no further deterioration in LVdP/dtmax, as observed in untreated dogs. More significantly, nifedipine caused a near normal recovery of both ATP and CP contents of the affected myocardium. Therefore, the present study shows that post-ischemic administration of nifedipine prevented reperfusion injury of the ischemic myocardium, as evidenced by both functional and metabolic recovery.