SGK1‐dependent salt appetite in pregnant mice

Aim:  Pregnancy is typically paralleled by substantial increase in maternal extracellular fluid volume, requiring net accumulation of water and NaCl. The positive water and salt balance is accomplished at least in part by increased uptake of salt secondary to enhanced salt appetite. Little is known about the underlying cellular mechanisms. Stimulation of salt appetite by mineralocorticoids, however, is known to be dependent on the serum‐ and glucocorticoid‐inducible kinase SGK1. Methods:  To test for a role of SGK1 in the stimulation of salt appetite during pregnancy, fluid intake was recorded in pregnant SGK1 knockout mice ( sgk1 −/− ) and their wild type littermates ( sgk1 +/+ ). The mice were offered two bottles, one with plain water and the other with isotonic saline. Results:  In early pregnancy, i.e. up to 10 days prior to parturition, the sgk1 +/+ mice displayed a significant preference for saline, whereas the sgk1 −/− mice preferred water. Accordingly, the water intake was significantly smaller and saline intake was significantly larger in sgk1 +/+ mice than in sgk1 −/− mice and the preference for water was significantly stronger in sgk1 −/− mice than in sgk1 +/+ mice. Plasma aldosterone levels were higher in sgk1 −/− mice than in sgk1 +/+ mice, a difference contrasting the enhanced salt appetite of sgk1 +/+ mice. Conclusions:  SGK1 participates in the stimulation of salt appetite during pregnancy.