The sodium/proton (Na/H) exchanger, Na,K-ATPase, and Ca2+-ATPase are membrane 
ion pumps whose basal activities may be regulated by local nongenomic actions of 
thyroid hormone and hormone analogues via a hormone receptor on plasma membrane 
integrin αvβ3. System A amino acid transport and the activity of P-glycoprotein 
(P-gp; ABCB1), a multidrug efflux pump, are also modulated by thyroid hormone 
and αvβ3. Where signal transduction has been studied, the presence of the 
hormone at the receptor is transduced by mitogen-activated protein kinase (MAPK) 
isoforms (ERK1/2; p38) or phosphatidylinositol 3-kinase into local actions. The 
existence of the cell surface receptor offers opportunities to pharmacologically 
modify actions of these important transport functions with nanoparticulate 
formulations of T4 and T3 that do not enter the cell. Such formulations may 
reverse complex intracellular accumulations of H+, Na+, and Ca2+ that occur in 
clinical settings such as ischemia. In addition, nanoparticulate 
tetraiodothyroacetic acid (tetrac), a thyroid hormone analogue that inhibits 
binding of T4 and T3 to integrin αvβ3 as well as certain other functions of the 
integrin, may reverse P-gp-dependent resistance to anti-cancer drugs in tumor 
cells.