title: Developmental changes in ventricular myosin isoenzymes of the tammar wallaby.
abstract: Ventricular myosin in eutherian mammals undergoes a perinatal change in response to a sharp rise in thyroid hormone levels during development. In this investigation, changes in ventricular myosin heavy chains (MyHCs) of the tammar wallaby (Macropus eugenii) from early pouch life to adulthood were analysed using native gel electrophoresis, SDS-PAGE and western blotting. Adult wallaby ventricle showed three myosin isoenzymes, V(1), V(2) and V(3); western blots using specific anti-alpha-MyHC and anti-beta-MyHC antibodies showed their MyHC compositions to be alphaalpha, alphabeta and betabeta, respectively. Ventricular muscle in early pouch joeys expressed predominantly beta-MyHC. Up to 200 days, the time of initial pouch exit, alpha-MyHC content was around 5%. Thereafter, there was a sharp increase of alpha-MyHC expression to 35% by 242 days of age, eventually falling back to 23% in the adult. These changes correlate with known surges in plasma levels of thyroid hormones around pouch exit. The results suggest that ventricular myosins in a marsupial mammal also undergo a developmental change, and that marsupial ventricular myosins are thyroid responsive as in eutherians. The increased alpha-MyHC expression empowers the heart to meet the enhanced cardiovascular demands of out-of-pouch activity and the thermogenic action of thyroid hormones.
authors.affiliation: Discipline of Physiology and the Bosch Institute, F13, School of Medical Sciences, Faculty of Medicine, The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Yoonah
authors.initials: Y
authors.lastname: Kim
authors.forename: Christine A
authors.initials: CA
authors.lastname: Lucas
authors.forename: Wendy W H
authors.initials: WW
authors.lastname: Zhong
authors.forename: Joseph F Y
authors.initials: JF
authors.lastname: Hoh
mesh_terms: D000818:Animals; D015153:Blotting, Western; D024722:Cardiac Myosins / Q000737:chemistry* / Q000502:physiology; D004591:Electrophoresis, Polyacrylamide Gel; D006352:Heart Ventricles / Q000201:enzymology*; D007527:Isoenzymes / Q000737:chemistry / Q000502:physiology; D007614:Macropodidae / Q000254:growth & development* / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D024722:Cardiac Myosins; D018995:Myosin Heavy Chains