Differential sensitivity of rat hepatocyte CYP isoforms to self-generated nitric oxide

Early loss of P450 in rat hepatocyte cultures appears directly related to n itric oxide (NO) overproduction. This study investigates the influence of e ndogenously generated NO (or NO-derived species) on the relative expression of cytochrome P450 (CYP) isoforms in rat hepatocytes. Our results support the view that loss of P450 holoenzyme in culture is the ultimate consequenc e of a NO driven process, activated during the common hepatocyte isolation procedure, that leads to an accelerated and selective degradation of specif ic CYP apoproteins, Under conditions in which NO and peroxynitrite formatio n is operative, changes in the level of specific CYP isoforms result in a s ignificant alteration of the CYP apoprotein profile that after 24 h of cult ure is quite different from that found in the liver of uninduced rats. This process is reverted by the early and efficient inhibition of NO synthesis, which allows for (1) maintenance of total P450 holoenzyme content, (2) pre servation of the initial constitutive CYP pattern in culture and (3) the ea rly expression of the normal inducibility in response to model inducers. (C ) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.