Changes associated with rat heart chromatin during cardiac hypertrophy.

Studies with N-Pyrenemaleimide, a probe which binds to H3 among histones and tryptophan residues of nonhistone proteins and subsequently emits fluorescence, showed that during developing cardiac hypertrophy, conformational changes due to DNA-histone interactions may be maximum at an early stage of hypertrophy (17% hypertrophy) while the changes due to non-histone protein(s) interactions may be maximum at a latter stage (28% hypertrophy). In vitro transcription analysis in isolated nuclei obtained from normal and hypertrophic hearts showed that nuclei obtained from 40% hypertrophic hearts had a maximum incorporation ability than nuclei obtained from 17% or 28% hypertrophic hearts. Analysis of histones and 0.35 M NaCl extractable nuclear proteins by single dimensional polyacrylamide gel electrophoresis did not reveal any changes in these proteins when obtained from normal and different stages of hypertrophic hearts. DNase I sensitivity studies with nuclei obtained from normal and hypertrophic hearts and with reconstituted nuclei, showed that changes in 0.35 M NaCl extractable proteins may contribute to the respective DNase I sensitivity of various hypertrophic nuclei. These studies also indicated that though nuclei obtained from 40% hypertrophic hearts showed maximum incorporation during in vitro transcription, the DNase I sensitivity is maximum only in nuclei obtained from 28% hypertrophic hearts and not from 40% hypertrophic hearts.