Ultrastructural changes in exocrine tissues of a DeltaF-508 CFTR mouse model

Cystic fibrosis (CF) is characterized by abnormal secretion from epithelial cells. We wanted to detect changes in the ultrastructural characteristics of cells within a number of exocrine tissues, including the colon, submandibular and parotid salivary glands of DeltaF-508 CFTR animals. Therefore, in the present study a DeltaF-508 CFTR mouse model was compared to control, by applying conventional and complex carbohydrates staining techniques to tissue sections at the electron microscope level. The colon of DeltaF-508 CFTR mice contained thick mucous secretions that harbored many bacteria, along with cytoplasmic fragments and leukocytes. Leukocytes were also seen to infiltrate the cytoplasm of goblet cells. Tissues were taken before, 10 min after isoprenaline, and 30 min after a further injection of methacholine. In the submandibular gland, there is limited secretory activity after isoprenaline treatment, and this increases further with methacholine treatment. Depletion of the secretory granules of acinar cells is observed, following the combined isoprenaline and methacholine treatment, but no significant changes in granule numbers occurred in granular tubule cells. Glycogen, abundant before treatment, is reduced within 10 min of isoprenaline treatment and is completely exhausted by 30 min, especially in the convoluted granular tubule cells. A few secretory granules in acinar and in granular tubule cells of the DeltaF-508 CFTR submandibular glands displayed two electron densities. The secretory responses of the parotid gland cells were similar to those in submandibular gland cells, except that in these DeltaF-508 CFTR cells, secretory granules appeared more polymorphic in structure than those found in control animals.