Volume expansion natriuresis during servo control of systemic blood pressure in conscious dogs.
The importance of arterial blood pressure (BP) and ANG II for the renal natriuretic response (NaEx) to volume expansion (3.5% body wt) was investigated during converting enzyme blockade (enalaprilate, 2 mg/kg). In separate experiments, BP was clamped either 30 mm Hg above or a few millimeters mercury below baseline by servo-controlled infusion of ANG II or sodium nitroprusside, respectively, so that volume expansion did not change BP. Enalapril decreased BP by 8 mm Hg. Without clamping, volume expansion returned BP to that of preenalapril control and increased NaEx 10-fold (40+/-10 to 377+/-69 micromol/min). During high pressure clamping (133+/-2 mm Hg), peak NaEx after volume expansion was 6% of control experiments. During low pressure clamping, NaEx was 68% of control experiments (45+/-15 to 256+/-64 micromol/min). The results show that 1) in absence of ANG II, volume expansion elicited pronounced natriuresis without increases in BP beyond baseline, 2) in the presence of hypertensive amounts of ANG II, the volume expansion-induced natriuresis was almost eliminated, and 3) nitroprusside prevented the increase in BP but not sodium excretion during volume expansion. ANG II appears to dominate the control of NaEx; however, when absent, volume expansion may still induce marked natriuresis even at constant BP, possibly via nitric oxide-mediated mechanisms.
Andersen
J L
JL
Department of Medical Physiology, University of Copenhagen, DK-2200 Copenhagen, Denmark.
Andersen
L J
LJ
Sandgaard
N C
NC
Bie
P
P
D000804:Angiotensin II / Q000097:blood / Q000494:pharmacology; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001127:Arginine Vasopressin / Q000097:blood; D001794:Blood Pressure / Q000502:physiology*; D001798:Blood Proteins / Q000032:analysis; D004231:Diuresis / Q000187:drug effects; D004285:Dogs; D004573:Electrolytes / Q000097:blood; D004656:Enalapril / Q000494:pharmacology; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D007668:Kidney / Q000187:drug effects / Q000502:physiology; D009318:Natriuresis / Q000187:drug effects*; D009599:Nitroprusside / Q000494:pharmacology; D009994:Osmolar Concentration; D010952:Plasma Substitutes / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology
D000806:Angiotensin-Converting Enzyme Inhibitors; D000959:Antihypertensive Agents; D001798:Blood Proteins; D004573:Electrolytes; D010952:Plasma Substitutes; D014665:Vasodilator Agents; D000804:Angiotensin II; D001127:Arginine Vasopressin; D009599:Nitroprusside; D004656:Enalapril