Mechanisms of the Renal Response to Plasma Volume Expansion

Abstract

Expansion of the plasma volume by infusions either of plasma or iso-oncotic albumin solution resulted almost uniformly in diuresis and natriuresis in anaesthetized dogs. Although the clearance of para-aminohippurate (RPF) usually increased, changes in clearance of creatinine (GFR) were neither large nor consistent in direction, indicating that the renal response depended on altered tubular reabsorption. The usual temporal dissociation between the peak values for water and sodium output during the response was interpreted as evidence of operation of two effector mechanisms. Reasons are given for believing that the renal response was not due to a direct action of the infusate, but rather to activation of a reflex mechanism by expansion of vascular volume. Bilateral cervical vagotomy did not prevent either the diuresis or the natriuresis, again implying that receptors additional to those in the cardiac atria must contribute to the sensory limb of the reflex. The average magnitude of diuretic and natriuretic responses after cervical vagotomy was, however, less than a quarter of that before the denervation, supporting the contention that the vagi do contribute to the renal response to expansion of the plasma volume when plasma is infused. The diuresis and the natriuresis still occurred during infusion in adrenalectomized animals, indicating that inhibition of aldosterone secretion is not the only effector mechanism leading to a natriuretic response to expansion of vascular volume.

Neither dorsal root nor baroreceptor afferents are necessary for eliciting the renal responses to acute intravascular volume expansion in the primate Macaca fascicularis.

“…Gilmore and Weisfeldt (1965) found that either bilateral vagotomy or carotid sinus denervation attenuated the diuretic but not the natriuretic response to acute intravascular volume expansion, whereas Pearce (1959) concluded that neither vagal nor carotid sinus pathways are necessary to elicit a natriuretic or diuretic response to the same stimulus. Atkins and Pearce (1959) later found that bilateral vagotomy significantly attenuated both the diuretic and natriuretic responses to acute intravascular volume expansion if the animals had not previously been hydrated. Although Pearce (1968) found that the chronic spinal dog (C 8 ) showed no diuresis or natriuresis in response to acute volume expansion, Michaelis and Gilmore (1969) still observed diuretic and natriuretic responses to volume expansion in the acute spinal animal (Cs), as did McDonald et al (1970) …”

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

“…With regard to the role of cardiac receptors in mediating the renal responses to outright volume expansion, it has been shown that cervical vagotomy, which interrupts vagally innervated cardiopulmonary receptor input to the central nervous system, attenuates the diuretic response to volume expansion in the dog (Atkins and Pearce, 1959;Gilmore and Weisfeldt, 1965), but fails to do so in the monkey (Gilmore et al, 1979). In addition, thoracic sympathectomy, which removes spinal sensory input from the cardiopulmonary region (Malliani, 1979), has no effect on the renal responses of the monkey to volume expansion (Cornish and Gilmore, 1983).…”

The effect of infusions of plasma and of saline on the renal response to water‐loading in sodium‐depleted dogs

“…If, as is believed by many, expansion of the total extracellular fluid volume can cause diuresis, then the graded expansion of this compartment induced by saline infusion would be more likely to cause a diuresis. Atkins & Pearce (1959), among others, have shown that infusion of 200 ml. of plasma causes a rise in urinary flow in normal dogs.…”