Differential Neural Control of Glomerular Ultrafiltration

Abstract

The renal nerves constrict the renal vasculature, causing decreases in renal blood flow (RBF) and glomerular filtration rate (GFR). Whether renal haemodynamics are influenced by changes in renal nerve activity within the physiological range is a matter of debate. We have identified two morphologically distinct populations of nerves within the kidney, which are differentially distributed to the renal afferent and efferent arterioles. Type I nerves almost exclusively innervate the afferent arteriole whereas type II nerves are distributed equally on the afferent and efferent arterioles. We have also demonstrated that type II nerves are immunoreactive for neuropeptide Y, whereas type I nerves are not. This led us to hypothesize that, in the kidney, distinct populations of nerves innervate specific effector tissues and that these nerves may be selectively activated, setting the basis for the differential neural control of GFR. In physiological studies, we demonstrated that differential changes in glomerular capillary pressure occurred in response to graded reflex activation of the renal nerves, compatible with our hypothesis. Thus, sympathetic outflow may be capable of selectively increasing or decreasing glomerular capillary pressure and, hence, GFR by differentially activating separate populations of renal nerves. This has important implications for our understanding of the neural control of body fluid balance in health and disease.

Residual renal function after partial or radical nephrectomy for renal cell carcinoma

“…24 The afferent arteriole resistance will be reduced by inhibition of angiotensin II, or by reducing the sympathetic input. 25 After removal of the renal tissue, GFR of the ipsilateral and/or contralateral kidney need to be increased to maintain fluid and electrolyte balance, through adjustments in vasomotor control of the microvasculature. 24 Following a nephrectomy, plasma volume will expand due to the decrease in renal excretory function.…”

Sex differences in postnatal growth and renal development in offspring of rabbit mothers with chronic secondary hypertension

“…First, neural stimulation of PRA may be increased, but other mechanisms may be counter-regulating this effect (i.e., tubuloglomerular feedback) in the prehypertensive phase in this model. Second, evidence suggests that at least two populations of functionally distinct nerves innervate the kidney (Type I and II) (14,16,17,37,38). We speculate that if it is Type I nerves that are increased in the female offspring (predominantly innervating the smooth muscle of the afferent arteriole), this might also explain why PRA is not increased.…”

Role of neuropeptide Y in the regulation of kidney function

“…Type I axons almost exclusively innervate the afferent arteriole, whereas type II axons are equally distributed on the afferent and efferent arterioles. Interestingly, NPY was located only in type II but not type I axons [42]. The functional significance of this finding and whether it may account for the preservation of GFR in the face of reduced RBF remain to be elucidated.…”

“…Indeed, this notion is compatible with the finding of Dietrich et al [35] in the split hydronephrotic kidney that NPY constricted only the very distal part of the afferent arteriole but not its larger more proximal part. Recently, it has been shown that the sympathetic innervation of the glomerulus consists of two distinct populations of axons, type I and II [42]. Type I axons almost exclusively innervate the afferent arteriole, whereas type II axons are equally distributed on the afferent and efferent arterioles.…”