FIGURE 1.

Hypo-osmolarity-induced activation of the β₁ integrin subunit in the perfused rat liver. Rat livers were perfused as described under “Experimental Procedures,” and liver samples were taken immediately before (t = 0 min) and after 1 min of hypo-osmotic perfusion (225 mosmol/liter). As indicated, the integrin antagonistic peptide GRGDSP (10 mmol/liter) was added 30 min prior to infusion of hypo-osmolarity. Immunoreactivity of the activated β₁ integrin subunit or the α₅β₁ integrin heterodimer was assessed by confocal laser scanning microscopy of frozen liver sections of the respective liver samples. In line with previous studies (10), hypo-osmolarity induced within 1 min the appearance of activated β₁ integrin immunoreactivity, suggesting activation of the integrin system in a GRGDSP peptide-sensitive manner (right panel). Immunoreactivity of the total α₅β₁ integrin heterodimer (left panel) remained unchanged under these conditions.