Role of the Carotid Bodies in the Hypertensive and Natriuretic Responses to NaCl Load in Conscious Rats

Abstract

Hyperosmotic challenges trigger a hypertensive response and natriuresis mediated by central and peripheral sensors. Here, we evaluated the importance of the carotid bodies for the hypertensive and natriuretic responses to acute and sub-chronic NaCl load in conscious rats. Male Wistar rats (250-330 g) submitted to bilateral carotid body removal (CBX) or sham surgery were used. One day after the surgery, the changes in arterial blood pressure (n = 6-7/group) and renal sodium excretion (n = 10/group) to intravenous infusion of 3 M NaCl (1.8 mL/kg b.w. during 1 min) were evaluated in non-anesthetized rats. Another cohort of sham (n = 8) and CBX rats (n = 6) had access to 0.3 M NaCl as the only source of fluid to drink for 7 days while ingestion and renal excretion were monitored daily. The sodium balance was calculated as the difference between sodium infused/ingested and excreted. CBX reduced the hypertensive (8 +/- 2 mmHg, vs. sham rats: 19 +/- 2 mmHg; p < 0.05) and natriuretic responses (1.33 +/- 0.13 mmol/90 min, vs. sham: 1.81 +/- 0.11 mmol/90 min; p < 0.05) to acute intravenous infusion of 3 M NaCl, leading to an increase of sodium balance (0.38 +/- 0.11 mmol/90 min, vs. sham: -0.06 +/- 0.10 mmol/90 min; p <0.05). In CBX rats, sub-chronic NaCl load with 0.3 M NaCl to drink for 7 days increased sodium balance (18.13 +/- 4.45 mmol, vs. sham: 5.58 +/- 1.71 mmol; p <0.05) and plasma sodium concentration (164 +/- 5 mmol/L, vs. sham: 140 +/- 7 mmol/L; p 0.05), without changing arterial pressure (121 +/- 9 mmHg, vs. sham: 116 +/- 2 mmHg). These results suggest that carotid bodies are important for the maintenance of the hypertensive response to acute hypertonic challenges and for sodium excretion to both acute and chronic NaCl load.