Salt intake and sensitivity of intestinal and renal Na+K+- ATPase to inhibition by dopamine in spontaneous hypertensive and Wistar-Kyoto rats

The present study evaluated the activity of jejunal Na+-K+-ATPase and its s ensitivity to inhibition by dopamine in spontaneous hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats during low (LS), normal (NS) and high (HS) sal t intake. Basal jejunal Na+-K+-ATPase activity in SHR on LS intake was high er than in WKY rats. Jejunal Na+-K+-ATPase activity in WKY rats, but not in SHR, on LS intake was significantly reduced (20% decrease) by dopamine (1 mu M) and SKF 38393 (10nM), but not quinerolane (10 nM), this being antagon ized the D-1 receptor antagonist (SKF 83566). Changing from LS to NS or HS intake in WKY rats increased basal jejunal Na+-K+-ATPase activity and atten uated the inhibitory effect of dopamine. In SHR, changing from LS to NS or HS intake increased basal jejunal Na+-K+-ATPase activity. Basal renal Na+-K +-ATPase activity in SHR on LS intake was similar to that in WKY rats and w as insensitive to inhibition by dopamine. Changing from LS to NS or HS inta ke in WKY rats increased basal renal Na+-K+-ATPase activity without affecti ng the inhibitory effect of-dopamine. In SHR, changing from LS to NS or HS intake failed to alter basal renal Na+-K+ AT-Pase activity. It is concluded that inhibition of jejunal Na+-K+ ATPase activity by D-1 dopamine receptor activation is dependent on salt intake in WKY rats, and SHR animals fail t o respond to dopamine, irrespective of their salt intake.