Cosegregation Analysis of Salt Appetite and Blood Pressure in Genetically Hypertensive and Normotensive Rats

Abstract

Enhanced sodium appetite is a robust behavioral characteristic of spontaneously hypertensive rats (SHR) which neither causes nor depends upon elevated blood pressure. However, the possibility remains that salt appetite and blood pressure are related by some unidentified common factor. The present study investigated the possible genetic co-determination of blood pressure and salt appetite in this animal model of hypertension.

Blood pressure of SHR, Wistar/Kyoto (WKY), and their F1 and F2 populations was measured prior to salt appetite testing by the tail cuff method. Sodium intake in these groups was measured daily for 5 days as the ad lib consumption of a 1.5% NaCl solution by subjects maintained on sodium deficient chow and demineralized water. Dynamic and stable components of salt appetite were identified in the parent strains and analyzed in the hybrid offspring.

The expected differences in blood pressure between SHR and WKY were observed, and the average blood pressure of the F1 and F2 groups fell roughly midway between SHR and WKY values. The SHR consumed substantially greater quantities of saline than WKY, but the F1 population consumed saline at a rate that was not different from WKY, rather than intermediate between SHR and WKY. There was no relationship in the F2 population between blood pressure and any measure of salt appetite. Thus, the high salt appetite and high blood pressure traits of SHR do not appear to share a common genetic basis. These results, considered with previously published work, suggest that approach and avoidance aspects of salt appetite may be separately inherited and also strongly suggest that neither is linked to hypertension.

Key Words:

• Genetic Analysis
• Hypertension
• Salt Appetite
• Sodium
• Blood Pressure
• SHR
• WKY
• Cosegregation