Longitudinal study of salt preferences in normotensive and hypertensive rats

To determine whether age-related changes in salt preferences occur over the lifespans of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY), the same animals of each genotype were tested as juveniles, and as young and older adults. Taste preference ratios for NaCl and KCl, at concentrations from 0.001 to 1.0 M, were calculated using 24-hour, two-bottle preference tests of each salt versus distilled water. Genotype exerted a significant effect on preference for both NaCl and KCl (p less than 0.0005). At each age and across concentrations, SHR had consistently higher preferences than did WKY. Few marked, age-related changes in overall preference for NaCl were noted within either strain, but juvenile and older adult SHR and WKY exhibited stronger preferences than did young adults for the higher concentrations of NaCl below the rejection threshold (p less than 0.001). Statistical age by concentration preference trends for KCl were similar to those for NaCl in SHR. Young adult WKY, however, had a significantly lower rejection threshold for that compound than did juveniles and older adults (p less than 0.001). These results indicate that genotype, age, salt type, and salt concentration can interact to influence salt preference in hypertension.