Effects of atrial natriuretic factor on renal handling of water and electrolytes in rats

Abstract

The intravenous injection of an extract of atrial myocardium into anesthetized rats during a hypotonic diuresis resulted in an increase in the renal excretion of water, sodium, potassium, calcium, magnesium, and phosphate. There was an increase in urine concentration which was probably a result of the secretion of vasopressin since it did not occur in Brattleboro (di/di) rats. A transient increase in glomerular filtration rate and renal plasma flow occurred during the first five minutes with a more sustained rise in filtration fraction. Injection of atrial extract also caused a partial inhibition of solute-free water formation in Brattleboro rats subjected to water diuresis and a partial inhibition of solute-free water reabsorption in rats subjected to maximal antidiuresis by infusing vasopressin. In neither case was the degree of inhibition as profound as that observed after injecting furosemide in a dose which caused a comparable natriuretic response. A large dose of furosemide blocked the natriuretic response to atrial extracts whereas, when a comparable level of sodium and water output was produced by massive infusions of saline, the natriuretic response to atrial extract was increased. It is suggested that atrial natriuretic factor might inhibit sodium transport in nephron segments beyond the medullary thick ascending limb. Furosemide might also act at the same tubular site or inhibit tubular secretion of the atrial natriuretic factor.

The effects of intravenous injection of .ALPHA.-human atrial natriuretic polypeptide on blood pressure, renal hemodynamics and urinary kinin excretion in anesthetized rabbits.

“…It has been reported that intravenous injection of atrial extracts produces a diuresis and kaliuresis of short duration (de Bold et al 1981;Borenstein et al 1983 ;Keeler and Azzarolo 1983 ;Vaughan et al 1983 ;Thibault et al 1984). These discrepancies of duration of diuresis and kaliuresis between in our experiment and in others might have been caused by the different volume status of animals.…”

“…However, glomerular filtration rate may have increased immediately after the intravenous injection of a-hANP, and this increase in GFR may have been transient, therefore, resulting in failure of determination for a period of 30 min after the a-hANP injection. In fact, Keeler and Azzarolo (1983) reported an increase in GFR only during the first 5-min period following the injection of atrial extract in spite of a fall in mean arterial pressure. There have been some different reports concerning the effects of atrial extracts on GFR.…”

“…Some studies have suggested an increase in renal blood flow (Keeler and Azzarolo 1983;Vaughan et al 1983), and others have indicated no effect on renal blood flow (Keeler 1982;Pollock and Banks 1983;Beasley and Malvin 1985). These conflicts of the mechanism of action of atrial extract include use of crude, unpurified extracts of the right atrium that may contain contaminants.…”

Renal mechanism of action of rat atrial natriuretic factor.

“…Within the last few years, a vasodilatory, natriuretic compound derived from granules within cardiocytes of the right atrium has been described (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16). This substance has been very recently characterized as a closely related group of peptides of 21-26 amino acids (2-4) derived from a common precursor polypeptide of 152 amino acids (3,5).…”

The effects of atrial natriuretic peptide on renal function and the renin-aldosterone system in anesthetized rabbits.

“…But the mechanism by which atrial extract or atrial natriuretic peptide produces a natriuresis and diuresis is still unclear. Some studies have suggested that contribution of an increase in renal blood flow (Keeler and Azzarolo 1983;Wakitani et al 1985) or glomerular filtration rate Maack et al 1984 ; Beasley and Malvin 1985;Huang et al 1985) to the natriuresis and diuresis, and others have indicated direct tubular effects (Briggs et al 1982; Sonnenberg et al 1982; Pollock and Banks 1983; Burnett et al 1984Burnett et al , 1986Hammond et al 1985).…”