Movement of horseradish peroxidase in rabbit submandibular glands after ductal injection

Horseradish peroxidase (HRP) has been used as a tracer to study movements of solutions injected retrogradely via the duct of submandibular glands in rabbits. 0.1 ml of solution was injected either manually or by a constant hydrostatic pressure, and the subsequent distribution of HRP in the gland and duct at different times after injection has been examined histochemically at light and electron microscopical levels. Shortly after the injections, strong interstitial staining for peroxidase resulted from passage between acinar cells. Some sites of cellular uptake were observed and staining occurred in some ductal cells even when the duct had been cut at the hilum to minimize pressure effects. It is not known whether this diffuse uptake represents a physiological or pathological phenomenon. Some interstitial activity still remained 24 hr after injection but had disappeared by 48 hr. Inflammatory cells first appeared in the gland about 4hr after the injection and slowly increased up to about 24 hr after injection. The results indiate that the HRP reaches the interstices of the gland principally by penetration between acinar cells, and that the junctional complexes between striated duct cells appear to be more resistant to disruption by luminal pressures.