Effect of mesenteric vascular congestion on reflex control of renal blood flow.
Portal hypertension initiates a splenorenal reflex, whereby increases in splenic afferent nerve activity and renal sympathetic nerve activity cause a decrease in renal blood flow (RBF). We postulated that mesenteric vascular congestion similarly compromises renal function through an intestinal-renal reflex. The portal vein was partially occluded in anesthetized rats, either rostral or caudal to the junction with the splenic vein. Portal venous pressure increased (6.5 +/- 0.1 to 13.2 +/- 0.1 mmHg; n = 78) and mesenteric venous outflow was equally obstructed in both cases. However, only rostral occlusion increased splenic venous pressure. Rostral occlusion caused a fall in RBF (-1.2 +/- 0.2 ml/min; n = 9) that was attenuated by renal denervation (-0.5 +/- 0.1 ml/min; n = 6), splenic denervation (-0.2 +/- 0.1 ml/min; n = 11), celiac ganglionectomy (-0.3 +/- 0.1 ml/min; n = 9), and splenectomy (-0.5 +/- 0.1 ml/min; n = 6). Caudal occlusion induced a significantly smaller fall in RBF (-0.5 +/- 0.1 ml/min; n = 9), which was not influenced by renal denervation (-0.2 +/- 0.2 ml/min; n = 6), splenic denervation (-0.1 +/- 0.1 ml/min; n = 7), celiac ganglionectomy (-0.1 +/- 0.3 ml/min; n = 8), or splenectomy (-0.3 +/- 0.1 ml/min; n = 7). Renal arterial conductance fell only in intact animals subjected to rostral occlusion (-0.007 +/- 0.002 ml.min(-1).mmHg(-1)). This was accompanied by increases in splenic afferent nerve activity (15.0 +/- 3.5 to 32.6 +/- 6.2 spikes/s; n = 7) and renal efferent nerve activity (32.7 +/- 5.2 to 39.3 +/- 6.0 spikes/s; n = 10). In animals subjected to caudal occlusion, there were no such changes in renal arterial conductance or splenic afferent/renal sympathetic nerve activity. We conclude that the portal hypertension-induced fall in RBF is initiated by increased splenic, but not mesenteric, venous pressure, i.e., we did not find evidence for intestinal-renal reflex control of the kidneys.
Hamza
Shereen M
SM
Department of Physiology, Univerity of Alberta, Edmonton, AB, Canada T6G 2S2.
Kaufman
Susan
S
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D003714:Denervation; D005728:Ganglia, Sympathetic / Q000502:physiology; D015171:Ganglionectomy; D007422:Intestines / Q000294:innervation / Q000502:physiology; D007668:Kidney / Q000294:innervation / Q000502:physiology; D008026:Ligation; D008297:Male; D008641:Mesenteric Vascular Occlusion / Q000503:physiopathology*; D009412:Nerve Fibers / Q000502:physiology; D017082:Portal Pressure / Q000502:physiology; D011169:Portal Vein / Q000502:physiology; D051381:Rats; D020318:Rats, Long-Evans; D012018:Reflex / Q000502:physiology; D012079:Renal Circulation / Q000502:physiology*; D013152:Splanchnic Circulation / Q000502:physiology; D013156:Splenectomy; D014690:Venous Pressure / Q000502:physiology