Heterogeneity of blood pressure responses to salt restriction and salt appetite in rats.

In contrast to a widely held belief, the response of blood pressure to even marked changes of salt (NaCl) intake is extremely heterogeneous in different strains of laboratory rats. Like in healthy humans, it is rather difficult to induce an increase or a decrease of blood pressure in normotensive rats by the manipulation of dietary salt consumption within a reasonable range. Moreover, severe NaCl restriction is sometimes associated with a paradoxical rise in blood pressure. No direct relation appears to exist between salt appetite and blood pressure. We showed that salt appetite was increased after dietary NaCl restriction in normotensive Wistar rats compared with normotensive Fischer 344 rats. The latter had a high renin status which was not sensitive to changes in dietary salt. An altered peripheral or central renin metabolism in this rat strain might be partly responsible for their relative lack of salt appetite and could be related to their notable lack of blood pressure sensitivity to dietary NaCl.