Relative protein, catalytic activities and/or mRNA levels of CYP2C12, CYP2A1, CYP2C6, CYP2C7, CYP2B1, IGF-1 and growth hormone receptor in livers from female rats treated with either diluent (controls) or octreotide. Rats fitted with our chronic indwelling atrial catheters (Pampori et al., 1991) were injected with either octreotide (25μg octreotide/kg body weight) or an equivalent volume of physiologic saline every 12 h for a total of 12 infusions. Relative levels were calculated by comparing all values to the control level with the highest isoform concentration (i.e., 100%). Values are means ± S.D. with a N=7. *P<0.01 compared to diluent-treated controls. Comparisons of expression levels between isoforms are not possible. In this regards, whereas CYP2C12 concentrations represent >40% of the total CYP in normal female rat liver, CYP2B1 is an inducible isoform expressed constitutively at only nominal levels (Ryan and Levin, 1993).