Fate of human albumin microsphere and spherocyte radioaerosols in the human tracheobronchial tree.
Human albumin microspheres (99mTc-HAM; 7-25 microns) and spherocytes (99mTc-S; 4-4.5 mu) are particles used for lung mucociliary clearance (MCC) measurements. If radiolabelled HAM aerosols are sent through an airway model to a screen, they appear peripherally distributed, whereas S present a more central and homogeneous distribution. The radioscanning evaluation of particle sedimentation in saline-filled tubes shows quite a different behavior pattern for S, HAM, and surfactant-coated HAM (S-C HAM). In these experimental conditions, S-C HAM and HAM floating properties were better than those of S. This could be explained by physical-chemical factors. Looking for the fate of organic particles after inhalation, we performed multiple bronchial biopsies in seven bronchitic patients, 2 h following inhalation of HAM and S. Scanning electron microscopy revealed that most of S was floating on the mucus layer, while HAM appeared deeply imbedded inside the mucus and partially digested. The same study performed on three bronchitic patients after S-C HAM inhalation, shows that S-C HAM float like S. In vitro, the time-course of tryptic digestion is similar for HAM and for S. However, in vivo, the different location of each particle on the bronchial surface might lead to a different digestion by trypsin and by PZ-peptidase, which are dosable in pathologic mucus. In our opinion, if HAM are coated with surfactant, this should improve the mucus-HAM interaction, thus helping to control variability in lung radioaerosol MCC studies.
Todisco
T
T
Pulmonary Division, University of Perugia, Italy.
Dottorini
M
M
Palumbo
R
R
Calvitti
M
M
Vernelli
C
C
Rossi
F
F
Iannacci
L
L
Grandolini
S
S
Cosmi
E V
EV
D000336:Aerosols; D001991:Bronchitis / Q000000981:diagnostic imaging; D004913:Erythrocytes, Abnormal; D006801:Humans; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D008953:Models, Anatomic; D009079:Mucociliary Clearance / Q000502:physiology*; D011877:Radionuclide Imaging; D012709:Serum Albumin; D013102:Spherocytes; D013667:Technetium
D000336:Aerosols; D012709:Serum Albumin; D013667:Technetium