Sections from perfused livers were analyzed for b1 immunoreactivity using antibodies recognizing the active b1 integrin subunit and the a5b1 integrin irrespective of its activation state (Schliess et al., 2004).
The a5b1 integrin in perfused rat liver is localized predominantly in the plasma membrane. Hypoosmolarity or insulin has no effect on the expression and localization of a5b1, but increases immunoreactivity of the activated b1 integrin subunit. The latter is largely confined to the plasma membrane, as indicated by superimposition of activated b1 and cortical actin staining. Furosemide, a loop diuretic inhibiting Na+/K+/2Cl~ cotransport, prevents the insulin-induced appearance of activated b1 immunoreactivity, but is without effect on a1b5 immunoreactivity and localization. This suggests that K+ uptake via the Na+/K+/2Cl~ cotransporter and hepatocyte swelling in response to insulin (Haussinger and Lang, 1992) trigger b1 integrin activation in perfused rat liver.
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