Strategy for uncovering complex determinants of hypertension using animal models

Vitamin B6: a molecule for human health?

Vitamin B₆ is an intriguing molecule that is involved in a wide range of metabolic, physiological and developmental processes. Based on its water solubility and high reactivity when phosphorylated, it is a suitable co-factor for many biochemical processes. Furthermore the vitamin is a potent antioxidant, rivaling carotenoids or tocopherols in its ability to quench reactive oxygen species. It is therefore not surprising that the vitamin is essential and unquestionably important for the cellular metabolism and well-being of all living organisms. The review briefly summarizes the biosynthetic pathways of vitamin B₆ in pro- and eukaryotes and its diverse roles in enzymatic reactions. Finally, because in recent years the vitamin has often been considered beneficial for human health, the review will also sum up and critically reflect on current knowledge how human health can profit from vitamin B₆.

Pyridoxine 5′-phosphate oxidase is a candidate gene responsible for hypertension in Dahl-S rats

To identify candidate genes responsible for hypertension in Dahl salt-sensitive rats (Dahl-S), an oligonucleotide microarray analysis was performed to find differentially expressed genes in kidneys of Dahl-S and Lewis rats. We obtained 101 F2 male rats from Dahl-S and Lewis rats and performed precise measurements of blood pressure (BP) and heart rate by telemetric monitoring at 14 weeks of age after 9 weeks of salt-loading. The correlation analysis between genotypes of differentially expressed genes and BP in F2 rats indicated that pyridoxine 5'-phosphate oxidase (Pnpo) and catecholamine-O-methyltransferease (Comt) showed a highly significant association with BP. However, in the case of Comt, the Dahl-S genotype correlated with low BP. Short/branched chain acyl-CoA dehydrogenase and Sah also showed a significant association with systolic blood pressure. The present study provided evidence that Pnpo is a candidate gene responsible for hypertension in Dahl-S rats.

Use of a panel of congenic strains to evaluate differentially expressed genes as candidate genes for blood pressure quantitative trait loci

Candidate gene(s) for multiple blood pressure (BP) quantitative trait loci (QTL) were sought by analysis of differential gene expression patterns in the kidneys of a panel of eight congenic strains, each of which carries a different low-BP QTL allele with a genetic composition that is otherwise similar to that of the hypertensive Dahl salt-sensitive (S) rat strain. First, genes differentially expressed in the kidneys of one-month-old Dahl S and salt-resistant (R) rats were identified. Then, Northern filter hybridization was used to examine the expression patterns of these genes in a panel of congenic strains. Finally, their chromosomal location was determined by radiation hybrid (RH) mapping. Seven out of 37 differentially expressed genes were mapped to congenic regions carrying BP QTLs, but only one of these genes, L-2 hydroxy acid oxidase (Hao2), showed the congenic strain-specific pattern of differential kidney gene expression predicted by its chromosomal location. This data suggests that Hao2 should be examined as a candidate gene for the rat chromosome 2 (RNO2) BP QTL.

New dopamine D2 receptor polymorphisms in rats and association with apomorphine-induced stereotypies

Adult Wistar rats injected with the dopamine receptor agonist apomorphine display different types of motility patterns with respect to oral stereotypes and locomotor activities. It was tested whether phenotypes exhibiting either 'sniffing' or 'non-sniffing' behaviour differed in gene structures of dopamine receptors D1 or D2. Forty-five Wistar rats of both genders were tested after a single dose of apomorphine (2 mg/kg s.c.) for stereotyped behaviour. Sequence analysis of the 5' flanking region, the 5' untranslated region and the coding region of the two genes revealed a new sequence for the 5' flanking region of the D1 receptor gene and two polymorphisms in the promoter region of the D2 receptor gene. The D2 receptor polymorphisms were denominated as T-355C- and A-257G-polymorphism. Between 'sniffing' and 'non-sniffing' animals no differences were detected in their D1 receptor sequence but there was a significant (P<0.05) association of the two phenotype groups with the D2 receptor genotype. These findings indicate that in Wistar rats at least part of an individual apomorphine stimulated behavioural phenotype might be due to an individual dopamine receptor D2 genotype.