Vesical-Renal Reflex: Diuresis and Natriuresis Activated by Intravesical Capsaicin

Abstract

In the last years the role of capsaicin sensitive innervation, in the activation of the micturition reflex, has been reported in many papers. In our experience, upon the intravesical administration of capsaicin in humans, we noticed an increase of diuresis. No interaction is known about the sensory innervation of the bladder and renal function, so we studied the possibility of the existence of a vesical-renal reflex arc. Twenty-one patients (9 men and 12 women) were randomised to receive intravesical infusion of saline solution containing 10 microM capsaicin. Urine output, glomerular renal filtrate (GRF) and effective plasma renal flow (EPRF), measured by Technetium-99m diethylenetetramine-penta-acetic acid (DTPA) renal scintigraphy, were recorded over twenty minutes before and after the intravesical administration of capsaicin. Urine density, [Na+] and [K+] concentration, and prostaglandin E2 excretion were also determined before and after intravesical administration of capsaicin or vehicle. Installation of saline solution containing 10 microM capsaicin produced a significant increase of mean urine output, an increase of GRF, of EPRF and of [Na+] and [K+] urine concentration. An increase, not statistically significant, was observed of PgE2 excretion. None of the patients treated with vehicle showed any modification of parameters examined. The present findings demonstrate a hitherto unrecognized effect: increased diuresis following selective chemical stimulation of bladder efferents with capsaicin. The renal diuretic response to intravesical capsaicin represents a working hypothesis about the possible involvement of a vesical-renal reflex arc organized at spinal or supraspinal level.

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“…It was showed a relationship between the capsaicin selective activation of bladder TRPV1and the increase of dieresis and natriuresis. These findings supported the hypothesis that TRPV1 was involved in the fluid homeostasis [Lazzeri et al 1995]. It is worth noting that in rats, capsaicin perfusion in one renal pelvis increased urine flow and urine sodium excretion in both kidneys.…”

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“…Moreover, the expression of TRPV1 in terminal nerves ending near to the mucosa and to the smooth muscle cells could indicate its involvement in maintaining the tone of the muscular layer [51], and the relationship between the capsaicin selective activation of bladder TRPV1 and the increase of dieresis and natriuresis supported the hypothesis of a TRPV1 involvement in fluid homeostasis [2]. …”

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“…This suggests the presence of a vesico-renal reflex, mediated by TRPV1 positive nerve fibers. 30 It appears that intravesical irritation promotes expulsion of the irritant, not only by increasing bladder contractility, but also by increasing diuresis.…”