Plasmapheresis affects responses of slowly and rapidly adapting airway receptors to pulmonary venous congestion in dogs.

Abstract

SUMMARY1. The effects of plasmapheresis on the responses of rapidly adapting receptors (RARs) and slowly adapting receptors (SARs) of the airways to pulmonary venous congestion were examined in dogs anaesthetized with a-chloralose. Pulmonary venous congestion was produced in a graded manner by partial obstruction of the mitral valve sufficient to raise the mean left atrial pressure by 5, 10 and 15 mmHg. Plasmapheresis was performed by withdrawing 10 % of blood volume twice.2. Both RARs (n = 11) and SARs (n = 5) responded to pulmonary venous congestion by increasing their activities. The responses of the former were proportionately greater.3. After plasmapheresis which reduced the concentration of plasma proteins by 12-3+1-0%, the responses of the RARs to pulmonary venous congestion were enhanced significantly. There was nio significant change in the responses of SARs.4. In another set of six RARs, the effects of graded pulmonary venous congestion were investigated twice with an interval of 45 min between the two observations. No significant differences were noted between the two responses.5. Collection of lymph from the tracheobronchial lymph duct (n = 6) showed that after plasmapheresis, there was an increase in the control lymph flow. In addition, the lymph flow was enhanced during pulmonary venous congestion (mean left atrial pressure increased by 10 mmHg).6. It is suggested that a natural stimulus for the excitation of the RAR is a function of the fluid fluxes in the pulmonary extravascular space.

Responses of slowly and rapidly adapting receptors in the airways of rabbits to changes in the Starling forces.

“…Previous investigations in anaesthetized dogs have shown that manoeuvres designed to increase Qf, i.e. pulmonary venous congestion and a reduction in plasma oncotic pressure, activated the RARs (Kappagoda & Ravi, 1989). Obstruction of the lymphatic drainage from the lung also activated these receptors (Ravi et al 1988).…”

“…The concentration of plasma proteins was reduced by batch plasmapheresis using procedures described previously (Kappagoda & Ravi, 1989). Approximately 10% of the circulating blood volume (estimated in the rabbit as 80 ml kg-') was withdrawn for this purpose.…”

“…If such is the case, selective manipulation of other factors which influence the rate of transvascular fluid flux across the pulmonary microvasculature (as defined by the Starling equation) may be expected to influence RAR activity also. Indeed, changes in oncotic pressure (Kappagoda & Ravi, 1989) and obstruction of the lymphatic drainage from the lung (Ravi, Teo & Kappagoda, 1988) were found to activate the RARs. Until now, the dog is the only species in which the influences of the factors which regulate fluid flux across the pulmonary vasculature have been examined in a systematic manner.…”

Substance P antagonist does not block the stimulation of rapidly adapting pulmonary stretch receptors by ammonia

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We investigated the effects of the substance P (SP) blocker 9]-SP on the response of rapidly adapting pulmonary stretch receptors (RARs) to SP administered into the right atrium, or ammonia vapor inhaled into the lungs in anesthetized, spontaneously breathing rabbits. Right atrial administration of SP (0.3, 1.0, and 3.0/xg/kg) caused an increase in the RAR activity, and this increase became more prominent as the dose of SP was increased.

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Lung congestion augments the responses of cells in the rapidly adapting receptor pathway to cigarette smoke in rabbit.

“…If so, this may explain the exaggerated respiratory responses to smoke in individuals with heart failure. It has been established that mild pulmonary venous congestion stimulates the pulmonary rapidly adapting receptors (RAR; Kappagoda, Man & Teo, 1987;Kappagoda & Ravi, 1989;Roberts et al 1993). It has also been demonstrated that inhalation of cigarette smoke stimulates the pulmonary vagal sensory receptors, in particular the RAR (Sellick & Widdicombe, 1971;Karlsson, Sant'Ambrogio & Widdicombe, 1988;Kou & Lee, 1990) and the pulmonary C fibre receptors (Lee et at.…”