Effects of vehicle, diet and gender on the expression of PMP70- and CYP2K1/2M1-like proteins in the mummichog

The mummichog (Fundulus heteroclitus) has been shown to be responsive to peroxisome proliferating agents (PPAs). Peroxisomes function as important sites for fatty acid β-oxidation. Peroxisome proliferation by PPAs or starvation can lead to changes in the size and number of peroxisomes and the expression of ω-hydroxylases (CYP2K1/2M1 in rainbow trout). Mummichogs were subjected to 96 h fasting or 96 h recovery from fasting. Expression of PMP70- and CYP2K1/2M1-like proteins in vehicle-treated or non-treated controls was compared in both males and females. Fasting and vehicle produced decreases in PMP70- and CYP2K1/2M1-like proteins in both males and females. In reproductive females, decreases due to fasting and vehicle treatment were greater than in female fish that were not gravid. Recovery from fasting resulted in levels of CYP2K1/2M1 near control levels in males while in recovered females, about 2-fold higher levels compared to controls were noted. These results indicate that gender, reproductive status and diet can produce changes in the expressed levels of peroxisomal PMP70 and microsomal CYP2K1/2M1-like proteins in the mummichog.