title: Expression of the brain and muscle isoforms of glycogen phosphorylase in rat heart.
abstract: Heart glycogen represents a store of glucosyl residues which are mobilized by the catalysis of glycogen phosphorylase (GP) and are mainly destined to serve as substrates for the generation of ATP. The brain isoform of GP (GP BB) was studied in rat heart in comparison with the muscle isoform (GP MM) to find functional analogies to the brain. Western blotting and quantitative reverse transcriptase polymerase chain reaction (RT-PCR) experiments revealed that at the protein level, but not at the mRNA level, the content of GP BB is similar in heart and brain. In contrast, GP MM is more abundant in the heart than in the brain. Immunocytochemically GP BB was colocalized with GP MM in cardiomyocytes. GP MM was also detected in interstitial cells identified as fibroblasts. The physiological role of co-expression of GP BB and GP MM in cardiomyocytes and in brain astrocytes is discussed in a comparative way.
authors.affiliation: Interfaculty Institute for Biochemistry, University of Tuebingen, Hoppe-Seyler-Str. 4, 72076 Tuebingen, Germany.
authors.forename: Heide
authors.initials: H
authors.lastname: Schmid
authors.forename: Brigitte
authors.initials: B
authors.lastname: Pfeiffer-Guglielmi
authors.forename: Benedikt
authors.initials: B
authors.lastname: Dolderer
authors.forename: Ulrike
authors.initials: U
authors.lastname: Thiess
authors.forename: Stephan
authors.initials: S
authors.lastname: Verleysdonk
authors.forename: Bernd
authors.initials: B
authors.lastname: Hamprecht