Abstract

An impaired endothelial-dependent vasorelaxation (EDV) precedes cerebrovascular lesions in an experimental animal model of inherited stroke, the stroke prone spontaneously hypertensive rat (SHRSP). Experiments performed in our laboratory suggest a genetic predisposition to EDV in this experimental model that segregates in the SHRSP/SHR F2 generation independently from blood pressure. The aim of the present study was to investigate the effects of genetic factors on EDV performing a random marker genome screening.

One-hundred thirty-seven F2 (64 male, 73 female) rats 6week-old and the parental strains were studied. Systolic blood pressure (SBP) was recorded and the vasodilator response to acetilcholine on rings from thoracic aorta pre-constricted with phenylephrine was assessed. The segregation of the fractional vasorelaxation (D ratio) in the F2 was chosen as quantitative phenotype. One-hundred microsatellites from a panel of markers polymorphic between SHR and SHRSP, spaced on average every 15 KcM along the rat genome, were tested. Data were expressed as mean±SEM; for each genotype marker one-way analysis of variance was carried out. Pearson test was used to assess a correlation between SBP and D ratio in the F2.

SBP (mmHg) was not different among the three groups (178±7 SHR, 180±6 SHRSP, 182±7 F2) and no correlation was found with D ratio (r=0.08, p=0.48); D ratio was reduced in the SHRSP compared to SHR (0.45±0.02 vs 0.75±0.02, p<0.05) and 0.64±0.03 in the F2 population, therefore the phenotypic variance genetically determined in this model is 94%. We have identified three markers located on chromosome 1, D1Wox4 (D ratio 0.71±0.03 SHR/SHR, 0.62±0.03 SP/SP, 0.58±0.03 SHR/SP, F2,119=3.7 p=0.027), chromosome 7, D7Wox4 (D ratio 0.71±0.04 SHR/SHR, 0.57±0.03 SP/SP, 0.60±0.03 SHR/SP, F2,119=3.5 p=0.032) and chromosome 14, D14Rat58 (D ratio 0.72±0.03 SHR/SHR, 0.54±0.04 SP/SP, 0.65±0.03 SHR/SP, F2, 82=3.8 p=0.026) influencing the D ratio with the SHR allele conferring a protective effect.

Our results strongly support a genetic predisposition to EDV in this experimental model and indicate that is influenced by at least three different genetic loci each one exerting a weak effect on the phenotype.

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