Analysis of metabolites in plasma reveals distinct metabolic features between Dahl salt-sensitive rats and consomic SS.13(BN) rats.

Salt-sensitive hypertension is a major risk factor for cardiovascular disorders. Our previous proteomic study revealed substantial differences in several proteins between Dahl salt-sensitive (SS) rats and salt-insensitive consomic SS.13(BN) rats. Subsequent experiments indicated a role of fumarase insufficiency in the development of hypertension in SS rats. In the present study, a global metabolic profiling study was performed using gas chromatography/mass spectrometry (GC/MS) in plasma of SS rats (n=9) and SS.13(BN) rats (n=8) on 0.4% NaCl diet, designed to gain further insights into the relationship between alterations in cellular intermediary metabolism and predisposition to hypertension. Principal component analysis of the data sets revealed a clear clustering and separation of metabolic profiles between SS rats and SS.13(BN) rats. 23 differential metabolites were identified (P<0.05). Higher levels of five TCA cycle metabolites, fumarate, cis-aconitate, isocitrate, citrate and succinate, were observed in SS rats. Pyruvate, which connects TCA cycle and glycolysis, was also increased in SS rats. Moreover, lower activity levels of fumarase, aconitase, α-ketoglutarate dehydrogenase and succinyl-CoA synthetase were detected in the heart, liver or skeletal muscles of SS rats. The distinct metabolic features in SS and SS.13(BN) rats indicate abnormalities of TCA cycle in SS rats, which may play a role in predisposing SS rats to developing salt-sensitive hypertension.

Angiotensin I-converting enzyme genotype influences arterial response to injury in normotensive rats.

Two normotensive strains of rat, the Lou and Brown Norway (BN) strains, have contrasting levels of plasma angiotensin-converting enzyme (ACE). To investigate the degree of genetic determination of ACE expression, a polymorphic marker of the ACE gene was analyzed in inbred rats of the two strains. The two inbred strains were shown to bear different alleles for a polymorphic marker at the ACE gene. The segregation of the alleles of this marker and the plasma ACE levels were studied in a group of F2 rats issued from a cross between Lou and BN rats. The degree of genetic determination of plasma ACE activity was estimated to be 94% in the F2 cohort. The ACE locus accounts for 74% of total plasma ACE variance. ACE activity and mRNA expression in lungs were also genetically determined. The difference observed in ACE mRNA accumulation in the lungs between the two strains was due to a difference in the transcriptional rate of the ACE gene, as shown in nuclear run-on experiments. No differences were observed in arterial blood pressure of homozygous F2 progeny. In these animals, ACE genotype did not interfere with the pressor or the depressor responses to ACE-dependent vasoactive peptides. There was a significant effect of strain on constitutive or inducible membrane or soluble ACE activity in primary cultures of vascular cells. Neointima formation in the carotid artery 14 days after balloon injury was also influenced by the genotype in F2 homozygous progeny, whereas the medial area was not. These results demonstrate that there is a close relationship between the genetically determined ACE expression and the inducibility of the ACE gene. The degree of genetic determination of ACE expression in inbred rat strains offers a unique opportunity to study the interaction between genetic and environmental determinants of ACE expression and its involvement in response to experimental cardiovascular and renal injury.

Allergic rhinitis model with Brown Norway rat and evaluation of antiallergic drugs.

An animal disease model of allergic rhinitis was developed with Brown Norway (BN) rat, a high immunoglobulin E responder strain. BN rats were immunized with ovalbumin (OA) and made to suffer from allergic rhinitis. The severity of allergic rhinitis was assessed by determining the extent of the three kinds of markers, Evan's blue, histamine and N-acetyl-beta-D-glucosaminidase, released into the nasal perfusate following the OA challenge to the nasal cavity of OA-sensitized BN rats. This experimental system was appreciated by antiallergic drugs; chlorpheniramine maleate inhibited the release of Evan's blue and elevated that of histamine, but did not affect the N-acetyl-beta-D-glucosaminidase level. Halopredone acetate inhibited the releases of all the three markers. The estimation of the released markers using allergic rhinitis brought about in BN rats was found to be a useful experimental system for evaluating the effect of drugs on allergic rhinitis.

Demonstration of the third kininogen in high and low molecular weight kininogens-deficient Brown Norway Katholiek rat.

A gel filtration profile of the plasma of Brown Norway Katholiek (B/N-Ka) rat was compared with those of B/N-Kitasato (B/N-Ki) and Sprague-Dawley (SD) rats. In the chromatograms of B/N-Ki and SD rat plasmas, high-molecular weight (HMW) kininogen was eluted together with pre-kallikrein. In lower molecular weight fractions, there were two kininogens, one of which released kinin by urinary kallikrein, snake venom kininogenase (SVK) and trypsin, and the other released kinin only by trypsin. In the chromatogram of B/N-Ka rat plasma, there was no fraction which released kinin by plasma kallikrein, urinary kallikrein or SVK. However, the kinin-release only by trypsin was found in the lower molecular weight fraction, which corresponds to the third peak of kininogen in the chromatograms of B/N-Ki and SD rat plasmas. These results indicate that B/N-Ka rat plasma is deficient in HMW kininogen, and also deficient in the LMW kininogen susceptible to urinary kallikrein and SVK, but it contains the third kininogen responsive only to trypsin.