The Neural Control of the Kidneys

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The neural control of the kidneys is through the sympathetic nervous system, efferent renal sympathetic nerves innervation and neuroeffector junctions have been identified along the renal vasculature, the tubules, the granular cells of juxtaglomerular apparatus (Kate etal, 2004; Edward etal, 2011). The action of sympathetic system is via the release the norepinephrine at sympathetic nerve terminals into the interstitial space. A moderately high levels of nerve stimulation has more effect on efferent arteriole than afferent thereby the RBF fall more than the GFR in consistent with efferent arteriolar constriction, however at maximal nerve stimulation afferent vasoconstriction predominates and leads to drastic reductions in both RBF and GFR (DiBona and Kopp, 1997; Edward etal, 2011). Unlike many other organs the kidneys have a low resting sympathetic tone, meaning that a decrease in sympathetic nervous system cannot effectively decrease the resistance. The main aim of sympathetic nervous system is to compensate for a fall in blood pressure or to prepare the body for the fight or flight response. Studies have investigated sympathepatic activity in relation to Protein resistriction by measuring norepinephrine (NE) turnover in heart and interscapular brown adipose tissue (IBAT) and reported an increase in sympathepatic activity (Laryssa etal, 1986; Martins etal, 2011 ), but since the Resting Sympathetic Activity has a very minimal effect on renal function any influence on it by dietary protein/amino acid will have little or no effect on kidney function.

Sympathetic tone was augmented in malnourished compared with control rats (131 ± 17 vs 41 ± 11 b.p.m., respectively), whereas parasympathetic tone was reduced in malnourished com...

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...prevented the rise in both GFR and RPF. Same study also examine whether the amino acid -induced hyperfiltration was due to dopamine release from renal nerves or enhanced renal tubule dopamine synthesis, they administered amino acid to rats in which the left kidney had been chronically denervated while the right kidney remained intact. It was observed that the infusion of amino acid led to significant increments in GFR and RPF only in the intact control kidney, whereas GFR and RPF remained unaltered in the denervated kidney.

Nitric oxide (NO) is another paracrine factor that act in kidney to modulate neurotransmission activity. It is produced via the action of nitric oxide synthase (NOS) enzymes this exist in three isoforms; neuronal (nNOS, NOSI), inducible (iNOS, NOSII), and endothelial (eNOS, NOSIII) and all are expressed within the kidney (Edward etal, 2011).

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