Changes in Na ⁺ and K ⁺ transport by the kidney when dietary Na ⁺ intake is low. + symbols indicate increased transepithelial movement of ions. Solid lines represent well-established signaling systems for regulating transport under these conditions. Dashed lines represent pathways that regulate transport but have not been shown to be involved in the response to reduced Na⁺ intake. The net result is that urinary Na⁺ excretion is reduced while K⁺ excretion remains constant.