Abstract

Methylation patterns of MHC (major histocompatibility complex) class I and vKi-ras (viral Kirsten-ras) homologous sequences in normal and adenomatous rat pituitary glands were studied as a function of age by Southern hybridization analysis using the isoschizomers Hpa II and Msp I. Both MHC class I and vKi-ras homologous sequences were found to be hypomethylated in a number of tumors, compared to normal pituitary gland tissue. However, despite reports indicating a general demethylation in mammalian tissues in relation to donor age, age-related methylation changes in this apparently methylation-unstable and cancer-prone organ were not observed.