Dietary sodium loading increases arterial pressure in afferent renal-denervated rats.
In rats fed high sodium diet, increasing renal pelvic pressure > or =3 mm Hg activates renal mechanosensory nerves, resulting in a renorenal reflex-induced increase in urinary sodium excretion. The low activation threshold of the renal mechanosensory nerves suggests a role for natriuretic renorenal reflexes in the regulation of arterial pressure and sodium balance. If so, interruption of the afferent renal innervation by dorsal rhizotomy (DRX) at T9-L1 would impair urinary sodium excretion and/or increase arterial pressure during high dietary sodium intake. DRX and sham-DRX rats were fed either a high or a normal sodium diet for 3 weeks. Mean arterial pressure measured in conscious rats was higher in DRX than in sham-DRX rats fed a high sodium diet, 130+/-2 vs 100+/-3 mm Hg (P<0.01). However, mean arterial pressure was similar in DRX and sham-DRX rats fed a normal sodium diet, 115+/-1 and 113+/-1 mm Hg, respectively. Steady-state urinary sodium excretion was similar in DRX and sham-DRX rats on high (17.9+/-2.2 and 16.4+/-1.8 mmol/24 h, respectively) and normal (4.8+/-0.3 and 5.0+/-0.4 mmol/24 h, respectively) sodium diets. Studies in anesthetized rats showed a lack of an increase in afferent renal nerve activity in response to increased renal pelvic pressure and impaired prostaglandin E2-mediated release of substance P from the renal pelvic nerves in DRX rats fed either a high or a normal sodium diet, suggesting that DRX resulted in decreased responsiveness of peripheral renal sensory nerves. In conclusion, when the afferent limb of the renorenal reflex is interrupted, a high sodium diet results in increased arterial pressure to facilitate the natriuresis and maintenance of sodium balance.
Kopp
Ulla C
UC
Department of Internal Medicine, Veterans Affairs Medical Center, and the Roy J. and Lucille Carver College of Medicine, University of Iowa, Bldg 3, Room 226, Highway 6W, Iowa City, IA 52246, USA. ulla-kopp@uiowa.edu
Cicha
Michael Z
MZ
Smith
Lori A
LA
D000284:Administration, Oral; D000344:Afferent Pathways / Q000601:surgery; D000818:Animals; D001794:Blood Pressure; D007668:Kidney / Q000294:innervation*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D019051:Rhizotomy; D012964:Sodium / Q000652:urine; D012965:Sodium Chloride / Q000008:administration & dosage / Q000494:pharmacology*
D012965:Sodium Chloride; D012964:Sodium