Primary effects of carotid chemoreceptor stimulation on gracilis muscle and renal blood flow and renal function in dogs.

Abstract

SUMMARY1. In chloralose-anaesthetized and artificially ventilated dogs, the carotid sinus regions were vascularly isolated and perfused either with arterial or mixed (arterial and venous) blood (partial pressure of 02 (PO2) 43 8 + 2-4 mmHg, mean + S.E.M. n = 14) to stimulate the carotid chemoreceptors. The carotid sinus pressure was held constant at 142-0 + 2-8 mmHg. Measurements were made of renal and gracilis muscle blood flow by wrap-round electromagnetic flow probes placed around the renal and gracilis arteries, glomerular filtration rate by creatine clearance, urinary sodium excretion by flame photometry and solute excretion by osmometry.2. In ten dogs, with intact cervical vagosympathetic trunks, carotid chemoreceptor stimulation produced significant increases in aortic pressure (AoP) of 12-7+ 1-1 % (n = 10, P < 0-001), in glomerular filtration rate (GFR) of 14-7+441 % (P < 0-001), urine flow rate (V) of 16-5+3-5% (P < 0002), in urinary sodium excretion (UNaV) of 17-5+2-5% (P < 0005) and in urinary osmolar excretion (UOSm V) of 13-2 + 22 % (P < 0-00 1), but a significant decrease in renal blood flow (RBF) of 5-8 + 1P8 % (P < 0 02). In six of these dogs in which gracilis muscle blood flow (MBF) was also recorded, carotid chemoreceptor stimulation caused significant increases in AoP of 12-8+P14% (n = 6, P < 0-001) and in MBF of 10-0+1-6% (P < 0 002), and a small but significant decrease in RBF of 3-6 + 1P5 % (P < 0-02).3. In fourteen dogs, with sectioned cervical vagosympathetic trunks, carotid chemoreceptor stimulation produced increases in AoP of 220 + 26 % (n = 14, P < 0-001), in GFR of 36-9 + 4-2 % (P < 0-001), in V of 301 + 4-4 % (P < 0-001 ), in UNaV of 31-4+5-3% (P < 0-001), and in UosmV of 25-7+5-8% (P < 0-001). However, it produced a greater decrease in RBF of 10-5 + 1P9 % (P < 0-001). In ten of these dogs, where MBF was recorded, carotid chemoreceptor stimulation caused greater increase in AoP of 22-4+3-0% (n = 10, P < 0-001) and in MBF of 32-8+3-7% (P < 0-001), and a greater decrease in RBF of 9-8+ 1-9% (P < 0-001).4. In fourteen dogs, with sectioned vagosympathetic trunks and controlled AoP, carotid chemoreceptor stimulation caused significant decreases in RBF of 19-1+1-6% (n = 14, P < 0001), in GFR of 17-7+2-2% (P < 0-001), in V of 23-4+2-5% (P < 0-001), in UNaV of 22-0+2-4% (P < 0-001) and in Uosm V of * To whom reprint request should be addressed. MS 9678AI. AL-OBAIDI AND F. KARIM 16 7 + 241 % (P < 0-001). In ten of these dogs, in which MBF was measured, carotid chemoreceptor stimulation produced a large decrease (a reverse effect) in MBF of 18 8+21 % (n = 10, P < 0)001) and in a further decrease in RBF of 19-7+2-0%