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PubMed1994

Localization of [D-Ala2]deltorphin I-like immunoreactivity in perinatal rat respiratory system.

The localization of [D-Ala2]deltorphin I, a delta-opioid receptor ligand, was studied in the lower respiratory tract of developing rats using an immunohistochemical method. [D-Ala2]-like immunoreactive cells were detected first in the principal bronchus as early as embryonic day 16. As embryos grew, positive cells became gradually visible everywhere from principal bronchi to respiratory bronchioles. The density of positive cells reached the highest level on embryonic day 21, but decreased gradually after birth. Positive cells were no longer seen on postnatal day 30 in any region of the airways. No positive cells were ever found in the trachea or alveoli of rats at any age studied. Ultrastructural examination indicated that the immunoreactive cells possessed a similar morphology to serous or Clara cells of the respiratory epithelium. Immunoreaction products tended to locate at the apical cytoplasm of positive cells. The results suggests that [D-Ala2]-like molecule(s) may be expressed transiently in serous cells or Clara cells, or both, of the rat bronchopulmonary tract. Such a molecule may act as a pulmonary growth-promoting or a differentiation-initiating factor in an early period of lung development.

Animals↗
PubMed1979

Organ-selective action of an antitumor drug: pharmacologic studies of liposome-encapsulated beta-cytosine arabinoside administered via the respiratory system of the rat.

beta-Cytosine arabinoside (Ara-C) in free and liposome encapsulated form was administered to Wistar rats by intratracheal institution. Free [3H]Ara-C administered in this manner rapidly left the lung and entered the systemic circulation. Liposome-encapsulated [3H]Ara-C persisted in the lung for a long period, with little redistribution to other tissues. Liposomes administered via the trachea became widely distributed throughout the lung air spaces, as evidenced by the histochemical localization of liposomes containing horse-radish peroxidase. Free Ara-C (5 mg/kg) administered into the trachea effectively suppressed macromolecular incorporation of [14C]thymidine ([14C]dThd) in the bone marrow and gut as well as in the lung. Liposome-encapsulated Ara-C (5 mg/kg) effectively suppressed macromolecular incorporation of [14C]dThd in the lung but had little effect on this process in the gut and bone marrow. Our results suggest that liposome-encapsulated Ara-C may be able to produce a local pharmacologic effect within the lung without producing adverse side effects in other tissues. This observation may be relevant to the chemotherapy of pulmonary metastases.

Animals↗