Internalization of fluorescent dextrans in the submandibular salivary glands of live animals: a study combining intravital two-photon microscopy and second harmonic generation

Here we show that a combination of two-photon microscopy and second harmonic generation can be successfully used to study endocytosis in the submandibular salivary glands of live animals. First, we have characterized the three-dimensional structure of the acini and the ducts forming the parenchyma of the excised glands by exciting various endogenous molecules, which highlight the shape of the cells and various components of the extracellular matrix. Next, by time-lapse imaging we show the dynamic distribution of fluorescent probes injected systemically. This was achieved by using a custom-made holder aimed to reduce the motion artifacts associated with the heartbeat and the respiration in the live animals. Finally, we show that fluorescent dextrans are internalized primarily by the supporting cells in the salivary glands, a characteristic shared by other secretory organs such as the pancreas.