Natriuretic Hormone

Abstract

The factors that control sodium excretion have been the subject of considerable work in recent years. The natriuresis that follows expansion of the extracellular fluid volume is mediated to a large extent by inhibition of tubular sodium reabsorption. Of the several mechanisms proposed to explain this inhibition, considerable interest has followed the suggestion that a humoral substance is released into the blood stream in response to volume expansion. The present article reviews the evidence for and against the existence of such a humoral substance (natriuretic hormone). It also discusses its proposed chemical nature and its possible site of origin in the organism as well as its mode of action.

Evidence that the Brain Participates in the Humoral Natriuretic Mechanism of Blood Volume Expansion in the Dog

“…We resorted to functional decapitation by a technique similar to that used by Cevese and Guyton (6) Studies by other investigators have implicated the brain as the source of the natriuretic factor. Klahr and Rodriguez (1) The absence of a significant natriuresis during acute blood volume expansion of intact dogs in the study of Cevese and Guyton (6) stands in sharp contrast to the marked natriuresis observed in our experiments and underscores several major differences between the experimental designs of the two studies. Cevese's and Guyton's experiments focused on the circulatory adjustments to an acute volume expansion stimulus administered as a pulse over 5 min.…”

“…Abstracts INTRODUCTION Expansion of the extracellular fluid volume elicits an increase in urinary sodium excretion. A large body of evidence implicates the participation of a humoral natriuretic factor in this response (1,2). Thus far, however, studies have failed to establish the identity and source of this factor, its mechanism of action, and its physiological role in the renal regulation of sodium balance.…”

An inhibitor of sodium transport in the urine of dogs with normal renal function.

“…Finally, and most critically, the presence of the inhibitor in the urine of patients and dogs with chronic uremia and of the present dogs with normal renal function appears to correlate with the dictates of maintaining external sodium balance. A number of other investigators have now demonstrated the presence of natriuretic factor(s) or inhibitor(s) of sodium transport in the blood of animals and man using whole animal experiments (13)(14)(15)(16)(17)(18)(19)(20)(21) or in vitro assays (13,18,20,(22)(23)(24)(25)(26)(27)(28)(29). Similarly, extracts of urine have also been shown to contain natriuretic substance(s) (16,17,19,20,(30)(31)(32)(33)(34)(35)(36) or inhibitor(s) of sodium transport (20,37,38).…”

Failure of Selected Endocrine Organ Ablation to Modify the Natriuresis of Blood Volume Expansion in the Dog

“…Increasing evidence implicates the participation of a humoral factor in this response (Klahr & Rodriguez, 1975). However, investigation has failed to establish the identity and source of the factor, its mechanism of action and its physiological role in the renal regulation of sodium excretion.…”