Histone and non-histone proteins from rabbit mammary gland at late pregnancy and early lactation. 
The content of non-histone protein in epithelial cell chromatin from rabbit mammary gland increased during late pregnancy and early lactation up to 30%, while the histone content remained unchanged.  No qualitative changes, as judged by polyacrylamide-gel electrophoresis, were found during accumulation of non-histone proteins at the onset of lactation.  The chromatin isolated at lactation, assayed either by polylysine or Toluidine Blue binding, contained slightly more available DNA-phosphate than the chromatin isolated at pregnancy.