PASSAGE OF A HETEROLOGOUS PROTEIN THROUGH ILEAL ENTEROCYTES OF NEWBORN PIGLETS - IMMUNOLABELING OF BOVINE SERUM-ALBUMIN AT THE LIGHT-MICROSCOPIC AND ELECTRON-MICROSCOPIC LEVEL

The passage of bovine serum albumin through ileum enterocytes of neona tal pigs was studied by light microscopy with indirect immunoperoxidas e and by electron microscopy with post-embedding direct immunogold met hods. Vacuoles filled with the heterologous protein were seen as early as 10 min after the administration of either bovine serum or solution s of bovine serum albumin by gavage. The sizes of vacuoles increased w ith time, their electron densities and immunoreactivities were at vari ance. The formation of albumin-containing vacuoles was independent of the concentration of the solutions fed, ranging from 1 to 7 %. Bovine serum albumin becomes discernible in the capillaries at 4 h after feed ing. By then, the intact albumin transported through enterocytes amoun ted to more than 10 % of the circulating plasma proteins. Of several t housand enterocytes screened in the whole study only one-from the pigl et 4 h after feeding-contained lysosomes.