Differential expression of A and B laminin chains during rat liver regeneration.

We have studied the distribution and expression of laminin during rat liver regeneration by immunofluorescence and immunoblotting using affinity-purified laminin antibodies. Laminin was localized on sinusoidal surfaces in normal and regenerating hepatic parenchyma, but enhanced expression was detected during regeneration from 6 hours to 7 days after a partial hepatectomy. A and B laminin chains were specifically detected by Western blotting in highly purified plasma membrane fractions derived from the sinusoidal domain of hepatocytes. Analysis of laminin expression in whole homogenates from hepatectomized rats showed a differential expression of A and B laminin chains during regeneration: The A chain showed a progressive increase, whereas the B chain exhibited an early, prereplicative increase and then gradually declined to control levels at the end of restorative growth. The results suggest differential temporal requirements for A and B laminin chains during hepatic growth and tissue formation.