Genetic analysis of alpha 2-adrenergic receptors and blood pressure using Dahl salt-sensitive rats.
OBJECTIVE
To evaluate the role of alpha 2-adrenergic receptors in genetic hypertension by cosegregation analysis using Dahl rats.


METHODS
Inbred Dahl salt-sensitive (SS/Jr) rats were crossed with inbred Dahl salt-resistant (SR/Jr) rats; also, SS/Jr rats were crossed with several control strains, and large F2 populations were subsequently produced from each cross. All F2 populations were raised on a high-salt diet. The rats were genotyped, where possible, at the loci for three different subtypes of alpha 2-adrenergic receptors designated as classes I, II and III. The blood pressures of the rats classified by genotype at each alpha 2-adrenergic receptor subtype locus were compared using analysis of variance.


METHODS
Genomic clones of three classes of alpha 2-adrenergic receptors were isolated from genomic lambda-phage libraries of SS/Jr or SR/Jr rat strains, or both, by screening with complementary DNA for human alpha 2-adrenergic receptors. Fragments of the rat genomic clones obtained were used for genotyping by restriction fragment length polymorphism. Also, cloned genomic DNA flanking the alpha 2-adrenergic receptors and containing microsatellites was sequenced; genotyping at informative microsatellite markers was performed using the polymerase chain reaction. Two of the three classes of rat alpha 2-adrenergic receptors were localized to rat chromosomes by linkage analysis or using a panel of mouse-rat hybrid somatic cell lines.


RESULTS
Rat alpha 2-adrenergic receptor classes I and III genes were assigned to rat chromosomes 14 and 3, respectively. These correspond to alpha 2-adrenergic receptor genes on human chromosomes 4 and 2, respectively. Extensive cosegregation analysis, involving five alleles in six segregating populations for class I alpha 2-adrenergic receptors, yielded no evidence of an effect of these loci on blood pressure. Classes II and III alpha 2-adrenergic receptors could each be tested in only one population and there was no evidence for an effect of either receptor gene on genetic differences in blood pressure. The dopamine-1B receptor was closely linked to the class I alpha 2-adrenergic receptor on rat chromosome 14. Thus, the negative cosegregation of the class I receptor with blood pressure applies equally to the dopamine-1B receptor.


CONCLUSIONS
Genetic analysis in segregating populations involving crosses of inbred Dahl salt-sensitive rats with five other strains provides no evidence for a genetic effect of class I alpha 2-adrenergic receptors, or of the dopamine-1B receptor, on blood pressure. Classes II and III alpha 2-adrenergic receptors also failed to cosegregate with blood pressure but, because only limited testing was possible with the classes II and III receptors, this negative result is not definitive.
Ginn
D I
DI
Department of Physiology and Biophysics, Medical College of Ohio, Toledo 43699.
Baptista
C A
CA
Alam
K Y
KY
Deng
A Y
AY
Dene
H
H
Le
H
H
Kurtz
T W
TW
Rapp
J P
JP
D000818:Animals; D001483:Base Sequence; D001794:Blood Pressure; D002874:Chromosome Mapping; D004351:Drug Resistance / Q000235:genetics; D006973:Hypertension / Q000139:chemically induced* / Q000235:genetics*; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes / Q000235:genetics; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000235:genetics*; D012965:Sodium Chloride
D015345:Oligonucleotide Probes; D011942:Receptors, Adrenergic, alpha; D012965:Sodium Chloride