Aims/hypothesis. Hypertriglyceridaemia is an important risk factor for coronary heart disease, especially in the context of the insulin resistance syndrome where it often occurs with hypertension. The two phenotypes are also associated in the hereditary hypertriglyceridaemic (hHTg) rat. The aim of this study was to map quantitative trait loci that affect plasma triglyceride concentration in the hHTg rat and determine whether they co-localize with loci for blood pressure. Methods. Second filial generation progeny (n=189) from a cross of the hHTg rat with the Brown Norway rat were phenotyped for fasting plasma triglyceride, glucose and insulin concentrations, and direct unrestrained resting blood pressure. A partial genome-scan was conducted using 153 microsatellite markers that were polymorphic between the two strains. Results. A major locus (lod score 6.5) influencing plasma triglyceride concentration in a co-dominant fashion was mapped to chromosome 4 between D1Mit5 and D1Mit17. Chromosome 8 contained multiple peaks with a lod score greater than 4.0 influencing triglyceride concentration. Importantly, none of the triglyceride loci had an effect on blood pressure. The triglyceride locus on chromosome 4 co-localized with a locus for fasting plasma insulin (lod score 4.1), although the effect on insulin concentration was in the opposite direction to that on triglyceride. Conclusion/interpretation. We have mapped the major loci that affect plasma triglyceride concentration in the hHTg rat. These loci do not influence blood pressure suggesting that these commonly associated phenotypes of the insulin resistance syndrome are not be due to pleiotropic effects of the same gene(s). [Diabetologia (2003) 46:352-358]

Activation of the sympathoadrenal system (SAS, comprising the sympathetic nervous system and the adrenal medulla) in response to stressful stimuli is an important defense mechanism as well as a contributor to several cardiovascular diseases. There is variability in the SAS response to stress, although the extent to which this is genetically regulated is unclear. Some rodent models, including the hereditary hypertriglyceridemic (hHTg) rat, are hyperresponsive to stress. We investigated whether quantitative trait loci (QTLs) that affect sympathoadrenal response to stress could be identified. Second filial generation rats (n = 189) derived from a cross of the hHTg rat and the Brown Norway rat had plasma norepinephrine (NE) and epinephrine (Epi) levels, indices of activation of the sympathoneural and adrenal medulla components, respectively, measured in the resting state and in response to an immobilization stress. Responses were assessed early (20 min) and late (120 min) after the application of the stress. A genome scan was conducted using 153 microsatellite markers. Two QTLs (maximum peak LOD scores of 4.17 and 3.52, respectively) influencing both the early and late plasma NE response to stress were found on chromosome 10. Together, the QTLs accounted for approximately 20% of the total variation in both the early and late NE responses in the F(2) rats. Interestingly, the QTLs had no effect on plasma Epi response to stress. These findings provide evidence for a genetic determination of the response of a specific component of the SAS response to stress. Genetically determined variation in sympathetic nervous system response to stress may contribute to cardiovascular diseases.

The major proportion of oral doses of 14C-mecinarone was excreted in the faeces by rat, dog and man, and in all species the faecal metabolites were more polar than mecinarone and the O-desmethyl reference compounds. Rat faecal extracts contained two major components each accounting for about 30-40% of the radioactivity. Dog and human faecal extracts contained some mecinarone but also three major, more polar components, two of which corresponded to the rat metabolites. Rat bile contained three major components and dog bile two components. One of the components in both bile samples was shown to be a conjugate of O-desmethyl-mecinarone. Besides mecinarone human urine contained a component corresponding to the phenol resulting from 0-demethylation in the p-methoxycinnamoyl group. The same two compounds were also detected in human plasma. The two major components in rat and dog faecal extracts gave mass spectra identical to mecinarone and the p-hydroxycinnamoyl derivative (O-desmethyl-mecinarone). It is postulated that these thermally-labile metabolites were formed by nucleophilic addition of a substituent to the alpha, beta-unsaturated ketone. It has been demonstrated in vitro that mecinarone forms a glutathione conjugate. The metabolites may be compounds of this type where the glutathione moiety has been degraded in the gastrointestinal tract.

1. After oral administration to dogs of the analgesic O-(diethylaminoethyl)-4-chloro[7-14C]benzaldoxime hydrochloride together with piperazine hydrochloride (2:1, w/w), at a dose of 4.5 mg/kg, the radioactivity was well absorbed and rapidly excreted. During 5 days, 81 percent of the dose (ca. 50 percent in 12 h) was excreted in urine and 10 percent in faeces. 2. Rates and routes of excretion of radioactivity were not altered in animals pre-treated with the drug for fourteen days. 3. Peak mean plasma concentrations of radioactivity (5.5 microgram equiv./ml) occurred at 90 min after an oral dose and were higher than those at 2 min following an equivalent intravenous (3.4 microgram equiv./ml) or rectal (4.0 microgram equiv./ml) dose which gave a max. at 45 min. 4. The drug was rapidly and extensively metabolized and no unchanged drug was detected in the plasma or urine. The major urinary metabolite was the N-oxide of the parent compound accounting for 34 percent and 23 percent dose excreted in the urine of males and females respectively during 12 h after administration.

Oral doses of the peripheral vasodilator mecinarone (6809 MD), administered as the 14C-compound, were well absorbed from the gastrointestinal tract of rats, dogs and humans. Much of the dose was excreted in 24 by rats and dogs, but more slowly by humans. In 5 days, rats, dogs and humans excreted in the urine and faeces respectively means of 3.3 and 95.9%, 13.2 and 80.3%, and 22.0 and 60.8%. The proportions of radioactivity excreted in urine and faeces after intravenous doses were similar to those after oral doses, means of 3.1 and 85.0% respectively by rats and 16.8 and 78.3% by dogs. Radioactivity present in the faeces was probably mainly excreted in bile; rats (n = 2) excreted a mean of 52.3, 19.8 and 3.9% in bile, faeces and urine after oral doses. Plasma concentrations of radioactivity after oral doses reached a maximum at 1 h in rats (mean 126 ng equiv/ml), at 1 to 2 h in dogs (mean 784 ng equiv/ml) and at 1.5 to 2 h in humans (mean 547 ng equiv/ml. Only a small proportion of this radioactivity (10-30%) represented unchanged drug. When "normalised" for dose/bodyweight differences, those levels were in the ratio 1 : 7 : 32 (rat less than dog less than man). Areas under plasma radioactivity concentration-time curves after oral doses to rats and dogs were about 25% and 53% respectively of those after corresponding intravenous doses. Only about 20% of the radioactivity in the plasma of dogs at 2 min after an intravenous dose represented unchanged drug. These data suggest that 6890 MD was probably rapidly biotransformed in rat, dog and man.