Effects of left atrial stretch in cardiac-denervated and intact conscious dogs

Abstract

We monitored cardiovascular and renal function in conscious dogs with surgically denervated hearts during two experimental procedures: 1) inflation of a balloon in the left atrium and 2) intravascular volume expansion. The results obtained were compared with results from identical experiments on sham-operated control dogs. Left atrial balloon inflation in the sham-operated dogs produced an increase in left atrial pressure, heart rate, urine flow, and sodium excretion; central venous pressure decreased. These changes were absent in the cardiac-denervated dogs. Infusion of 6% dextran in isotonic saline (16% of estimated blood volume) increased the heart rate significantly in the control dogs but not in the cardiac-denervated dogs; other hemodynamic measurements were comparable in the two groups. Urine flow and sodium excretion increased significantly in both the cardiac-denervated and control dogs; the responses did not differ significantly between the two groups. These experiments demonstrate that inflation of a balloon in the left atrium of a conscious dog elicits diuretic and natriuretic responses that are dependent on intact cardiac neural pathways, presumably specifically dependent on afferent neural impulses from left atrial receptors. On the other hand, an increase in circulating blood volume induced by the intravenous infusion of an isotonic, isoncotic solution elicits diuretic and natriuretic responses in the cardiac-denervated dog that are similar to the renal responses produced in a control dog. Thus, although cardiac receptors are capable of eliciting reflex changes in both hemodynamics and renal function, it is not clear what role they play in mediating the renal responses evoked by increases in blood volume.

A Highly Sensitive and Rapid Radioimmunoassay for the Determination of Argmine8-Vasopressin

“…The present assay can therefore be considered as both highly sensitive, and more rapid than other assays. Isoosmotic arginine 8 -vasopressin suppression by central volume stimulation during water immersion (30,31) was clearly demonstrated in accordance with the findings of other groups, supporting the concept of inhibition of arginine 8 -vasopressin secretion by acute atrial distension (32,33).…”

Renal responses of the cardiac-denervated nonhuman primate to blood volume expansion.

“…When comparing our results only with studies that also utilized an intrapericardial surgical denervation it appears that, even in the dog, cardiac receptors are not necessary for eliciting the renal responses to volume expansion. Kaczmarczyk et al (1981) and Fater et al (1982) both demonstrated that cardiac denervation abolished the diuretic and natriuretic responses to localized atrial stretch but did not affect the responses to volume expansion. In contrast, Mulcahy et al (1973Mulcahy et al ( , 1975, in two separate studies, reported that volume expansion caused an exaggerated diuresis (Mulcahy et al, 1973) and natriuresis (Mulcahy et al, 1975) in cardiac-denervated dogs.…”

“…For example, it has been demonstrated that atrial type B receptors are less sensitive in the monkey than in the dog, in that their discharge rate changes little with increases in atrial pressure (Zucker and Gilmore, 1975). Furthermore, localized increases in left atrial pressure or atrial stretch, induced by either inflation of a balloon in the left atrium or tightening of a mitral snare, leads to a diuresis and natriuresis in the dog (Gauer and Henry, 1976;Linden, 1976;Kaczmarczyk et al, 1981;Fater et al, 1982), but fails to elicit any renal effects in either the anesthetized (Gilmore and Zucker, 1978) or conscious monkey (Cornish and Gilmore, 1982).…”

Natriuresis caused by blood volume expansion in dogs is not mediated by the renal nerves

“…The effects of atrial distention have not always been studied in the same way. These methods include small balloons inside either atrium (Henry et al 1956;Ledsome et al 1961;Fater et a!. 1982), rapid atrial pacing (Goetz & Bond, 1973;Boykin, McDonald & Schrier, 1975) and the method we have employed, of intravenous volume loading adopted from Gilmore (1968).…”