Insulin epithelial permeability

An increased epithelial permeability of hydrophilic compounds, that is terbutaline (Mw 225 Da), 99mTc-labelled diethylene triamine penta-acetate (99mTc-DTPA Mw 492 Da), 113mln-labelled biotinylated DTPA (Mw 1,215 Da) and insulin, has been demonstrated in smokers as compared to non-smokers [8, 62, 84, 127, 159],... 

Yamamoto A, Tanaka H, Okumura S, Shinsako K, Ito M, Yamashita M, Okada N, Fujita T, Muranishi S (2001) Evaluation of insulin permeability and effects of absorption enhancers on its permeability by an in vivo epithelial system using Xenopus pulmonary membrane. Biol Pharm Bull 385-389... 

Glucose penetrates most tissues slowly unless insulin is present to facilitate its uptake however, central nervous system (CNS) cells, capillary endothelial cells, gastrointestinal epithelial cells, pancreatic cells, and renal medullary cells are freely permeable to glucose. 

Ahsan, F., et al. 2003. Effects of permeability enhancers, tetradecylmaltoside and dimethyl-beta-cyclodextrin, on insulin movement across human bronchial epithelial cells (16HBE14o ). Eur J Pharm Sci 20 27. 

Just recently a series of other quaternized chitosan derivatives have been synthesized and characterized, namely, A,A-dimethyl, A-ethyl chitosan (DMEC) (Bayat et al. 2006), A-methyl, A,A-diethyl chitosan (DEMC) (Avadi et al. 2004) and A,A,A-triethyl chitosan (TEC) (Avadi et al. 2003). In a comprehensive study (Sadeghi et al. 2008a, b) the four quaternized derivatives of chitosan, trimethyl chitosan (TMC), diethylmethyl chitosan (DEMC), triethyl chitosan (TEC) and dimethylethyl chitosan (DMEC) with degree of substitution of approximately 50% were synthesized and their effect on the permeability of insulin across intestinal Caco-2 monolayers was studied and compared with chitosan both in free-soluble form and in nanoparticulate systems. Trans-epithelial electrical resistance (TEER) studies revealed that all four chitosan derivatives in free-soluble forms were able to decrease the TEER value in the following order TMC>DEMC>TEC = DMEC>chitosan, indicating their... 

---