Studies comparing in vivo : in vitro metabolism of three pharmaceutical compounds in rat, dog, monkey, and human using cryopreserved hepatocytes, microsomes, and collagen gel immobilized hepatocyte cultures

The in vivo metabolism of three pharmaceutical compounds, EMD68843, EMD9678 5, and EMD128130, was compared in fresh and cryopreserved hepatocyte (CPH) suspensions and microsomes from rat, dog, monkey, and human livers and fres h human and rat hepatocyte collagen gel immobilized cultures (GICs). Half o f the major in vivo metabolites was produced by phase 1 (hydroxylation, oxi dation, hydrolysis, N-dealkylation) and half by phase 2 metabolism (mostly glucuronidation but also sulfation and glycine conjugation). The identity a nd percentage of phase 1 and 2 metabolites from each compound produced in h epatocytes compared well with that in each species in vivo. Glucuronidation was more extensive in GICs than in CPHs. In contrast, CPHs but not GICs, p roduced sulfate metabolites. Microsomes (supplemented with NADPH only) prod uced most of the phase 1 but no phase 2 metabolites. Metabolism in CPHs was the same as in fresh hepatocyte suspensions. Discrete species differences in metabolism were detected by CPHs and microsomes. Cytochrome P450 and glu curonosyl S-transferase contents of CPHs did not account for species differ ences in the percentage of phase 1 and 2 metabolites or the rate of disappe arance of the parent compounds in these cells. These data show a good corre lation between major metabolites formed in vivo and in vitro. CPHs and GICs , unlike microsomes, carried out sequential phase 1 and 2 metabolism. Each in vitro system has its own advantages, however, for short-term metabolism studies CPHs may be more useful since they are readily available easier and quicker to prepare than GICs, and have more comprehensive enzyme systems t han microsomes.