Chronically reserpinized rat as a model for cystic fibrosis: Na+ transport inhibitory effect in submaxillary saliva.

The retrograde perfusion assay in the rat parotid gland was used to investigate the effects of salivary secretions from control and reserpine-treated rats on Na+ reabsorption. Results demonstrated that submaxillary saliva from the treated animals caused a 69% inhibition of Na+ reabsorption, accompanied by a 28% reduction in the volume of saliva secreted, and a 22% reduction in flow rate. By contrast, submaxillary saliva from control rats caused a 6% inhibition of Na+ reabsorption, a 6% reduction in volume, and a 5% reduction in flow rate. Parotid saliva from reserpine-treated rats also inhibited Na+ reabsorption to the extent of 39% and caused a 38% reduction in volume and a 33% reduction in flow. Parotid saliva from control rats only inhibited Na+ reabsorption to the extent of 2.7% and caused a 4--6% reduction in salivary volumes and flow rates. The inhibition of Na+ reabsorption and the reduction in salivary volume and flow rates caused by submaxillary saliva of reserpine-treated rats were either abolished or significantly reduced when the saliva was previously heated to 100 degrees C, frozen, and then thawed or kept in glass tubes at 4 degrees C for 24 hr. These results indicate that saliva from reserpine-treated rats have comparable effects in this assay system to those of saliva from cystic fibrosis (CF) patients and further support its use as an animal model for this disease.