Initial lung deposit

Houpert, P., Chazel, V., Paquet, F., Henge-Napoli, M.H., Anso-borlo, E. (1999). The effects of the initial lung deposit on uranium biokinetics after administration as UF4 and U04. Int. J. Radiat. Biol. 75 . ... 

Animal species Aerosol form AMAD (ftfn) Age at Exposure No. animals Deposition Initial lung Reference... 

Dry powder inhalers have initially found their application in inhalation therapy as a CFC-free alternative for the older MDIs. However, nowadays they seem to have a much larger potential [14,53], because of the high lung deposition that can be attained and also because they are suitable for the pulmonary delivery of therapeutic peptides and proteins [2,10,16]. 

Examples of radiolabeling MDIs for lung deposition studies are given in Table 1. Historically, there are three major methods of radiolabeling suspension MDIs, developed by Few, Short, and Thomson, Newman et al. ° and Kohler, Fleischer, Matthys. The first two were initially developed for polymeric particles but were later modified for drugs. 

Organic Lead. Following a single exposure to vapors of tetraalkyl lead compounds (approximately 1 mg/m3 breathed through a mouthpiece, 10-40 breaths of approximately 1 L volume) in four male subjects, 37% and 51% of inhaled tetraethyl and tetramethyl lead, respectively, were initially found in the respiratory tract, but a considerable percentage of these volatile compounds was lost through exhalation (Heard et al. 1979). Approximately 60-80% of the deposited tetraalkyl lead was absorbed by the lungs. 

Particle deposition in the respiratory tract can initiate inflammatory responses. With repeated deposition, inflammation becomes chronic, and the site or sites of deposition beeome laden, not only with the particulates, but with several types of cells—fibroblasts, macrophages, leukocytes, and lymphocytes. These cells are normal constituents of the lung, an organ composed predominantly of connective tissue. Lung connective tissue forms the thin membrane that defines the functional alveolar-capillary unit. Inside this air sac and on the membrane are specialized eells required for gas exchange, maintenance, and repair (Fig. 3.6). 

---