Control of right atrial pressure at constant cardiac output suppresses volume natriuresis in anesthetized rats

Ackermann, Uwe; Rudolph, John R.

doi:10.1139/y84-131

Cited by 17 publications

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“…Many investigators have reported that AP immunoreactivity (APir) release appears to be stimulated by atrial distension through acute volume expansion both in animals (2,3,7,8) and in humans (4)(5)(6)(7)(8)(9). Removal of right atrial appendages in anesthetized rats attenuated the urinary volume (UV) and urinary sodium excretion (UNaV) in response to volume expansion (10).…”

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Paradoxical relationship between atriopeptin plasma levels and diuresis-natriuresis induced by acute volume expansion.

Sakata

Greenwald

Needleman

1988

Proc. Natl. Acad. Sci. U.S.A.

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Surgical removal of one or both atrial appendages was employed in rats to reduce the intrinsic stores of atriopeptin (AP). In conscious rats (with intact baroreceptor reflexes), bilateral or unilateral atrial appendectomy suppressed the diuresis and natriuresis produced by acute volume expansion. Surprisingly, volume expansion (with 4% bovine serum albumin in saline at 1.5 ml/kg per min for 15 min) did not result in an increase in plasma AP immunoreactivity (APir) in control or atrial-appendectomized conscious rats. Previous studies demonstrated that acute volume expansion in anesthetized animals caused increased plasma APir. Indeed, we found that volume expansion causes comparable diuresisnatriuresis in conscious and chloral hydrate-anesthetized rats, but only the latter group exhibits an increase in plasma APir. Brattleboro rats, which are deficient in vasopressin, exhibit the same response as Long-Evans controls in that acute volume expansion in conscious animals produces a pronounced diuresis and natriuresis but no APir release, but when these same animals are anesthetized, there is a simultaneous induction of diuresis-natriuresis and APir release by volume expansion. Plasma AP does not increase in conscious rats despite a large volume load, 3040% of the total blood volume given in 15 min, and the natriuresis-diuresis appears to also be independent of vasopressin. On the other hand, the diuresis induced by acute volume expansion in anesthetized rats seems dependent on the elevated APir, since rats made autoimmune to AP (which are nonresponsive to exogenous AP infusions) exhibit a diuresis in conscious but not anesthetized rats. We therefore conclude that the participation of AP in volume homeostasis is more likely in pathophysiological states and that another mechanism or possibly another atrial factor mediates the diuresis-natriuresis induced by volume expansion in conscious rats.Atrial distension produced by elevation of atrial pressure or head-out water immersion (1), volume expansion (2-5), and administration of pressor agents (1, 6) lead to release of atriopeptin (AP) from the atria. Many investigators have reported that AP immunoreactivity (APir) release appears to be stimulated by atrial distension through acute volume expansion both in animals (2,3,7,8) and in humans (4-9). Removal of right atrial appendages in anesthetized rats attenuated the urinary volume (UV) and urinary sodium excretion (UNaV) in response to volume expansion (10).Similarly, conscious rats 2 weeks after bilateral atrial appendectomy exhibited reduced UV and UNaV during volume expansion (11 In the present study we examined the changes in plasma APir in atrial appendectomized rats. We decided to perform these experiments in conscious precannulated animals because we had observed that basal plasma APir levels were considerably higher in chloral hydrate-anesthetized animals compared to unanesthetized controls. The choice of these conditions led us to an unanticipated finding: the diuresis caused by volume expansion of conscio...

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confidence: 99%

Paradoxical relationship between atriopeptin plasma levels and diuresis-natriuresis induced by acute volume expansion.

Sakata

Greenwald

Needleman

1988

Proc. Natl. Acad. Sci. U.S.A.

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“…Recent studies in the rat have investigated the hemodynamic signals that induce the release of ANF. Increments in atrial pressure and/or volume have been reported (7,8) to promote sodium and water excretion. In addition, experiments in anesthetized (9) and conscious (10) rats have indicated that the natriuretic and diuretic responses to acute expansion of the intravascular volume were blunted in rats with prior removal of the atrial appendages.…”

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Effects of Atrial Appendectomy on Circulating Atrial Natriuretic Factor during Volume Expansion in the Rat

Villarreal

Freeman

Davis

et al. 1986

Experimental Biology and Medicine

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This study examined the changes in the circulating level of endogenous atrial natriuretic factor during diuresis and natriuresis produced by acute volume expansion in anesthetized rats with either bilateral atrial appendectomy ( n = 9) or sham operation ( n = 9). Following control measurements in the sham-operated rats, 1 % body weight volume expansion with isotonic saline produced an increment in urinary sodium excretion of over 4 peqlmin ( P < 0.05) while urine volume increased by more than 20 pl/min ( P < 0.05). These responses were associated with a significant increase in immunoreactive plasma atrial natriuretic factor from a baseline value of 82 2 10 pg/ml to a level of 120 f 14 pg/ml (P < 0.05). In contrast, in the group of rats with bilateral atrial appendectomy an identical degree of volume expansion increased urinary sodium excretion and urine volume by only 0.61 peq/min (P < 0.05) and 3.07 pl/min (P < 0.05), respectively. In this group, immunoreactive plasma atrial natriuretic factor remained statistically unchanged from a control value of 70 k 12 pg/ml to a level of 82 k 16 pg/ml (P > 0.05).Comparison of the two groups indicates that the natriuresis, diuresis, and plasma atrial natriuretic factor levels during volume expansion were significantly reduced in the rats with bilateral atrial appendectomy. No differences in mean arterial pressure and heart rate were observed between the two groups. These data demonstrate that removal of both atrial appendages in the rat attenuated the release of atrial natriuretic factor during volume expansion; and this effect, in turn, was associated with a reduction in the natriuretic and diuretic responses. o 1986 Society for Experimental Biology and Medicine.

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Atrial natriuretic peptide response to ionic and nonionic contrast left ventriculography

Roman

et al. 1990

Clinical Cardiology

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Summary:Atrial natriuretic peptide (ANP) levels were measured prior to and at 1 and 5 minutes postcontrast left ventriculography with an ionic contrast agent (diatrizoate), and a nonionic agent (iopamidol) and the results were compared. Since ionic contrast agents have been found to cause an increase in left ventricular end-diastolic pressure (LVEDP) and nonionic agents have been found to have less of an effect on LVEDP, we investigated the response of ANP levels, which have been found to increase secondary to increased LVEDP (atrial pressure), with both agents. A group of 38 patients who were scheduled for left heart catheterization for suspected coronary artery disease was included (19 in each group) and blood samples for ANP levels were drawn from the left ventricle. At the same time, heart rate, LVEDP, and left ventricular systolic pressure (LVSP) were also measured. It was found that the LVEDP increased significantly for both agents at 1 minute postventriculography, but no further change occurred at 5 min. Heart rate increased significantly in the diatrizoate group at 1 minute with a return of heart rate to preventriculography levels at 5 min, while the ANP level and LVSP remained unchanged at 1 minute postventriculography with both agents but increased significantly at 5 min in the diatrizoate group only. This difference in ANP response is not correlated with the LVEDP. The response of ANP may be related to heart rate and/or LVSP.

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Control of right atrial pressure at constant cardiac output suppresses volume natriuresis in anesthetized rats

Cited by 17 publications

References 0 publications

Paradoxical relationship between atriopeptin plasma levels and diuresis-natriuresis induced by acute volume expansion.

Paradoxical relationship between atriopeptin plasma levels and diuresis-natriuresis induced by acute volume expansion.

Effects of Atrial Appendectomy on Circulating Atrial Natriuretic Factor during Volume Expansion in the Rat

Atrial natriuretic peptide response to ionic and nonionic contrast left ventriculography

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