99mTc isonitrils biophysical aspects in pulmonary tuberculosis. Part II. In vitro evaluation of 99mTc MIBI cellular uptake mechanism.

UNLABELLED: The aim of this experimental work was to assess the uptake of 99mTc MIBI (metoxy-isobutil-isonitril) on Mycobacterium tuberculosis (MT) cultures, and to compare this uptake level with the uptake of two normal cell types in culture (fibroblasts and myocytes), and with MT membrane fluidity. MATERIAL AND METHOD: Mycobacterium tuberculosis cultures were realised on Lowenstein Jensen medium by standard methodology. Normal cells were neonatal rat heart myocytes and fibroblasts. Final plating was done to have an almost complete cell monolayer the day of the experiment, in culture dishes. The cells were incubated with a 1.85 kBq/ml concentration of 9mTc MIBI, at 37 degrees C, using three dishes for each cell type. A three point kinetic (15, 60 and 90 minutes) was realised. Static polarization of fluorescence with Diphenylhexatrien (DPH) fluorescent marker of Mycobacterium tuberculosis in suspension (concentration 10(4)/ml NaCl 9 per thousand) was realized. RESULTS: Mycobacterium tuberculosis have high 99mTc MIBI uptake, 106,47% (compared with the known higher normal uptake cells--the myocytes, considered 100%); the highest uptake kinetic point is at 15 minutes radiotracer incubation. The assessment of Mycobacterium tuberculosis wall fluidity has not brought conclusive results. CONCLUSION: Our results could give informations to understand the Mycobacterium tuberculosis 99mTc MIBI uptake mechanisms in in vivo lesions.