A Review of the Characteristics and Research Applications of Spontaneously Hypertensive Rats (SHR)
1. Background and Naming Standards
Spontaneously Hypertensive Rats (SHR) are one of the most important genetic models for hypertension in medical research. This strain originates from Wistar rat populations, characterized by stable white fur. As a gold standard model for primary hypertension research, SHR rats' most notable feature is that all individuals spontaneously develop hypertension, making them ideal subjects for studying human primary hypertension and its complications.
In academic literature, the standardized naming of this strain should include both the complete English name and abbreviation "SHR." It is worth noting that different research institutions may use similar expressions such as "Spontaneous Hypertensive Rat" or "Spontaneously Hypertensive Rat," but according to original literature records, "Spontaneously Hypertensive Rats" was indeed the correct nomenclature initially adopted by Okamoto's research team.
2. Development History and Breeding Process
2.1 Initial Screening Phase The breeding work for this strain began in the early 1960s under Professor Kozo Okamoto's team at Kyoto University School of Medicine in Japan. The research team selected individuals with spontaneous hypertensive characteristics from Wistar rat populations as a breeding foundation. Specific screening criteria included selecting male individuals whose tail vein systolic pressure reached 150-175 mmHg at seven weeks old to pair with slightly higher systolic pressure female individuals (140-150 mmHg).
It is noteworthy that this blood pressure screening was not completed once; rather, it gradually reinforced hypertensive traits through multiple generations of selective breeding over more than 20 generations.
2.2 Inbreeding Line Establishment Process With increasing generations of inbreeding, researchers observed three significant trends: first, an intergenerational increase in hypertension incidence; second, an earlier onset age for developing hypertension; most importantly, a continuous rise in severe hypertensives (>200 mmHg). After systematic close-inbreeding selection processes were conducted, a homozygous line with a 100% incidence rate was ultimately obtained.
This breeding process was officially published by Okamoto and Aoki in 1963 but had been preliminarily reported at several academic conferences between 1961-1962. The National Institutes of Health (NIH) introduced this strain into America in 1969, making it an internationally recognized experimental animal model.
2.3 Parent Strain Traceability The Wistar rat population used for initial screening has unique genetic backgrounds due to being imported from America's Wistar Institute to Tokyo University back in 1938 before reaching Hokkaido University (1944) then finally arriving at Kyoto University's Animal Center (1951). During long-term maintenance through close-inbreeding practices these rats underwent genetic differentiation from their original Wistar counterparts hence they are specifically referred to as “Wistar Kyoto” rats (WKY). This special genetic background provided critical foundations necessary for successfully cultivating SHR strains.
3. Physiological Features and Pathological Manifestations
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