HUMAN INSULIN DIFFUSION PROFILE THROUGH A LAYER OF CACO-2 CELLS

The Caco-2 human colon adenocarcinoma cell line undergoes a spontaneou s differentiation in culture to enterocytic cells. The diffusion of hu man insulin through a layer of the enterocytic differentiated Caco-2 c ell line was studied using a polycarbonate membrane as a mechanical su pport. Human insulin (100 U) was dissolved in Dulbecco's Modified Eagl e's Medium (DME) and placed on the apical side of the cells grown in c ulture, and allowed to diffuse under sink conditions for a period of 2 4 hr (37 degrees C, pH = 7.4). Samples were collected from the receive r side at 0.5, 1, 2, 3, 4, 5, 6, 7, 8, and 24 hr. The samples were the n analyzed for insulin content using an HPLC method. The calculated ap parent permeability coefficient (P-app) for human insulin through the cells was (6.5 +/- 1.2) x 10(-7) cm/sec, mean +/- SE, n = 8. We conclu de that using a Caco-2 cell line to study the diffusion of insulin thr ough the intestinal barrier may be an alternative to other in vivo or in situ methods.