Role of 99mTc-mannitol and 99mTc-PEG in the assessment of paracellular integrity of cell monolayers.
OBJECTIVE
To assess the role of 99mTc-mannitol and 99mTc-polyethylene glycol 4000 in the evaluation of paracellular integrity of Caco-2 and Madine-Darby canine kidney (MDCK) cell monolayers, and confirm it in the presence of absorption promoters.


METHODS
Radiolabelling of mannitol and polyethylene glycol was performed by a simple reduction method. Transepithelial electrical resistance values were measured to gain information regarding the integrity of tight junctions of Caco-2 and MDCK cell monolayers. Permeabilities of 99mTc-mannitol/99mTc-polyethylene glycol across cell monolayers were studied in the absence and presence of absorption promoters, namely dimethyl-beta-cyclodextrin, chitosan hydrochloride and sodium lauryl sulfate, and during recovery studies to assess paracellular integrity.


RESULTS
Values for the apparent permeability coefficient (Papp) of Tc-mannitol were found to be 0.286 x 10 cm x s(-1) and 0.507 x 10 cm x s(-1) in Caco-2 and MDCK cell monolayers, respectively, whereas corresponding values for 99mTc-polyethylene glycol were 0.046 x 10 cm x s(-1) and 0.065 x 10 cm x s(-1). The insignificant Papp values of the marker molecules demonstrated the paracellular integrity of the cell monolayers. Significant increases in the Papp values in the presence of absorption promoters and their combinations due to opening of paracellular pathways and a return of Papp values to almost baseline values during recovery studies confirm the role of these marker molecules in the assessment of paracellular integrity of cell monolayers.


CONCLUSIONS
99mTc-labelled marker molecules can be attractive, useful and viable alternatives to the conventionally used markers in the assessment of paracellular integrity because of the absence of tissue-damaging corpuscular radiation and the ease of production of radiochemically pure and stable molecules at a reasonable cost.
Shah
Pranav J
PJ
Department of Pharmacy, Faculty of Technology & Engineering, Institute of Nuclear Medicine and Allied Sciences, New Delhi, India.
Jogani
Viral V
VV
Mishra
Pushpa
P
Mishra
Anil K
AK
Bagchi
Tamishraha
T
Misra
Ambikanandan R
AR
D000818:Animals; D018938:Caco-2 Cells; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004285:Dogs; D017097:Electric Impedance; D006801:Humans; D008353:Mannitol / Q000493:pharmacokinetics*; D010539:Permeability; D011092:Polyethylene Glycols / Q000493:pharmacokinetics*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D013667:Technetium / Q000493:pharmacokinetics*; D019108:Tight Junctions / Q000378:metabolism*
D019275:Radiopharmaceuticals; D008353:Mannitol; D011092:Polyethylene Glycols; D013667:Technetium