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 sensitivity to inhibition by dopamine in spontaneous hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats during low (LS), normal (NS) and high (HS) salt intake. Basal jejunal Na+-K+-ATPase activity in SHR on LS intake was higher 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 antagonized 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 attenuated 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 was insensitive to inhibition by dopamine. Changing from LS to NS or HS intake in WKY rats increased basal renal Na+-K+-ATPase activity without affecting 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 to respond to dopamine, irrespective of their salt intake.