Different expression of renin-angiotensin system components in hearts of normotensive and hypertensive rats

Tissue renin-angiotensin systems are known to behave differently from the circulating renin-angiotensin system (RAS). It has already been proposed that not only the circulating RAS, but also RAS localized in the cardiac tissue plays an important role in the heart failure. The objective of this study was to compare the gene expression of individual components of the renin-angiotensin system in hearts of normotensive and hypertensive rats. Two genetically hypertensive rat strains--spontaneously hypertensive rats (SHR) and hereditary hypertriglyceridemic rats (HTG)--were compared with Wistar-Kyoto (WKY) and Lewis (LEW) normotensive controls. In addition, developmental changes in gene expression of individual components of cardiac RAS were studied in 20-day-old fetuses, 2-day-old newborns and 3-month-old HTG and LEW rats. In our study, the angiotensinogen gene expression did not differ either among adult normotensive and hypertensive strains, or during development. In contrast, the renin gene expression was significantly increased in hearts of hypertensive compared to normotensive rats. Moreover, a 5-fold increase of renin mRNA was observed in hearts of HTG rats between day 2 and the third month of age. There was also an age-dependent increase of ACE gene expression in both HTG and LEW rats which was substantially delayed in HTG hearts. In conclusion, the results of our study suggest that overexpression of the cardiac renin gene in hypertensive strains could participate in the structural and functional changes of the heart during the development of hypertension.     

The association study of DRD2, ACE and AGT gene polymorphisms and metamphetamine dependence

We investigated the association between metamphetamine dependence and TaqI A polymorphism of the dopamine receptor D2 gene (DRD2), I/D polymorphism in angiotensin-converting enzyme (ACE) and M235T polymorphism of the angiotensinogen gene (AGT) in 93 unrelated metamphetamine-dependent subjects and 131 controls. Our results did not prove any association of TaqI A polymorphism of the DRD2 gene, I/D polymorphism of ACE gene, and M235T polymorphism of AGT gene with the metamphetamine dependence in Caucasians of Czech origin. However, a significant difference in allele I frequency between male and female control groups for the I/D ACE polymorphism (p<0.03) was found.     

Terguride attenuates prolactin levels and ameliorates insulin sensitivity and insulin binding in obese spontaneously hypertensive rats

Glucose tolerance, serum insulin, insulin receptors in epididymal fat tissue, circulating total cholesterol and triglyceride concentrations as well as serum prolactin were studied in obese and lean spontaneously hypertensive rats (SHR) of both sexes. Obese animals displayed insulin resistance and elevated insulin and triglyceride concentrations. Moreover, in obese rats the increased mass of epididymal fat tissue was accompanied with decreased capacity of high affinity binding sites of insulin receptors in the tissue plasma membranes. Terguride treatment lowered prolactin serum levels which was accompanied by ameliorated insulin sensitivity in obese animals of both sexes. In addition, terguride treatment decreased serum insulin and triglyceride concentrations in obese females and at the same time enhanced the affinity of high affinity insulin binding sites. Our results show that obesity in SHR is associated with a decreased capacity of insulin receptors and that prolactin may play a role in obesity-induced insulin resistance, particularly in female rats.     

Wine polyphenols improve cardiovascular remodeling and vascular function in NO-deficient hypertension

The effects of the red wine polyphenolic compounds (Provinol) on hypertension, left ventricular hypertrophy, myocardial fibrosis, and vascular remodeling were investigated after chronic inhibition of nitric oxide (NO) synthase by administration of N(G)-nitro-L-arginine methyl ester (L-NAME) to rats. Rats were divided into four groups: a control group, a group treated for 4 wk with L-NAME (40 mg x kg(-1) x day(-1)), and two groups treated with L-NAME followed by 3 wk of either spontaneous recovery or recovery with Provinol treatment (40 mg x kg(-1) x day(-1)). Administration of Provinol produced a greater readiness of the decrease in blood pressure than that in the spontaneous recovery group. Provinol significantly depressed myocardial fibrosis and expedited the decrease in aortic cross-sectional area, the increase in endothelium-dependent relaxation, and the decrease in contraction of the aorta. These effects of Provinol were associated with a greater increase of NO synthase activity in the left ventricle and the aorta. The present study provides evidence that Provinol accelerates the regression of blood pressure and improves structural and functional cardiovascular changes produced by chronic inhibition of NO synthesis.     

Hypoxic fetoplacental vasoconstriction in humans is mediated by potassium channel inhibition

Fetal to maternal blood flow matching in the placenta, necessary for optimal fetal blood oxygenation, may occur via hypoxic fetoplacental vasoconstriction (HFPV). We hypothesized that HFPV is mediated by K(+) channel inhibition in fetoplacental vascular smooth muscle, as occurs in several other O(2)-sensitive tissues. With the use of an isolated human placental cotyledon perfused at a constant flow rate, we found that hypoxia reversibly increased perfusion pressure by >20%. HFPV was unaffected by cyclooxygenase or nitric oxide synthase inhibition. HFPV and 4-aminopyridine, an inhibitor of voltage-dependent K(+) (K(v)) channels, increased pressure in a nonadditive manner, suggesting they act via a common mechanism. Iberiotoxin, a large conductance Ca(2+)-sensitive K(+) (BK(Ca)) channel inhibitor, had little effect on normoxic pressure. Immunoblotting and RT-PCR showed expression of several putative O(2)-sensitive K(+) channels in peripheral fetoplacental vessels. In patch-clamp experiments with smooth muscle cells isolated from peripheral fetoplacental arteries, hypoxia reversibly inhibited K(v) but not BK(Ca) or ATP-dependent currents. We conclude that human fetoplacental vessels constrict in response to hypoxia. This response is largely mediated by hypoxic inhibition of K(v) channels in the smooth muscle of small fetoplacental arteries.     

DNA adduct formation from quaternary benzo[c]phenanthridine alkaloids sanguinarine and chelerythrine as revealed by the 32P-postlabeling technique

Using the 32P-postlabeling assay, we investigated the ability of quaternary benzo[c]phenanthridine alkaloids, sanguinarine, chelerythrine and fagaronine, to form DNA adducts in vitro. Two enhanced versions of the assay (enrichment by nuclease P1 and 1-butanol extraction) were utilized in the study. Hepatic microsomes of rats pre-treated with beta-naphthoflavone or those of uninduced rats, used as metabolic activators, were incubated in the presence of calf thymus DNA and the alkaloids, with NADPH used as a cofactor. Under these conditions sanguinarine and chelerythrine, but not fagaronine, formed DNA adducts detectable by 32P-postlabeling. DNA adduct formation by both alkaloids was found to be concentration dependent. When analyzing different atomic and bond indices of the C11-C12 bond (ring B) in alkaloid molecules we found that fagaronine behaved differently from sanguinarine and chelerythrine. While sanguinarine and chelerythrine showed a preference for electrophilic attack indicating higher potential to be activated by cytochrome P450, fagaronine exhibited a tendency for nucleophilic attack. Our results demonstrate that sanguinarine and chelerythrine are metabolized by hepatic microsomes to species, which generate DNA adducts.     

Phylogeographical approaches to assessing demographic connectivity between breeding and overwintering regions in a Nearctic-Neotropical warbler (Wilsonia pusilla)

We characterized the pattern and magnitude of phylogeographical variation among breeding populations of a long-distance migratory bird, the Wilson's warbler (Wilsonia pusilla), and used this information to assess the utility of mtDNA markers for assaying demographic connectivity between breeding and overwintering regions. We found a complex pattern of population differentiation in mitochondrial DNA (mtDNA) variation among populations across the breeding range. Individuals from eastern North America were differentiated from western individuals and the eastern haplotypes formed a distinct, well-supported cluster. The more diverse western group contained haplotype clusters with significant geographical structuring, but there was also broad mixing of haplotype groups such that no haplotype groups were population specific and the predominance of rare haplotypes limited the utility of frequency-based assignment techniques. Nonetheless, the existence of geographically diagnosable eastern vs. western haplotypes enabled us to characterize the distribution of these two groups across 14 overwintering locations. Western haplotypes were present at much higher frequencies than eastern haplotypes at most overwintering sites. Application of this mtDNA-based method of linking breeding and overwintering populations on a finer geographical scale was precluded by the absence of population-specific markers and by insufficient haplotype sorting among western breeding populations. Our results suggest that because migratory species such as the Wilson's warbler likely experienced extensive gene flow among regional breeding populations, molecular markers will have the greatest utility for characterizing breeding-overwintering connectivity at a broad geographical scale.