By mating is successive generations only those animals that failed to develop hypertension from salt ingestion,a resistant strainhas been evolved in which consumption of large quantities of salt fails to influence the blood pressure significantly.In contrast,by mating only animals that quickly develop hypertension from salt,a sensitive strainhas also been developed.
The availability of these tow strains permits investgations not heretofore possible.They provide a plausible laboratory model on which to investigate some clinical aspects of the human prototypes of hypertension.More important,there might be the possibility of developing methods by which genetic susceptibility of human beings to high blood pressure can be defined without waiting for its appearance.Radioactive sodium 22 was an important tool in working out the characteristics of the sodium chloride metabolism.
1.The study of the effects of salt on high blood pressure was carried out ______.
a.as members of the same family tend to use similar amounts of salt
b.to explore the long-term use of a sodium based substance
c.because it was proven that salt caused high blood pressure
d.because of the availability of chemically pure salt and its derivatives
2.The main difference between S and R rats is their ______.
a.need for sodium 22
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