title: Sex differences in rat heart. Different patterns of catalytically active creatine kinase isoenzymes.
abstract: OBJECTIVE
  We hypothesized that the anaerobic ATP synthesis mediated by the creatine kinase/phosphocreatine (CK/PCr) system is sexually dimorphic during maturation and aging of the rat heart.
  
  
  BACKGROUND
  Gender-related morphological and functional differences in cardiovascular aging seem to explain the greater longevity of mammalian females, including women.
  
  
  METHODS
  By means of heart CK specific activity and cytosolic CK isoenzyme analyses we studied 46 male and female Wistar rats of similar weight divided in groups of 200, 250, and 300 g of body weight.
  
  
  RESULTS
  No sex differences were observed in heart weight and post 27,000 x g heart protein content at any studied weight. Heart/body weight ratios did not show any significant gender difference along the study. Differences of heart CK specific activity were found only at 257 +/- 6 g of rat body weight due to a decrease of the male enzyme activity. The female heart showed a larger variety of cytosolic CK isoenzymes at any studied weight. Heavily catalytically stained BB-CK type cytosolic isoenzymes were consistently found in the heart of rats of either sex at the studied weights, contrarily to the accepted view of CK tissue specificity.
  
  
  CONCLUSIONS
  In this work, significant gender differences were mainly found in the patterns and number of catalytical cytosolic CK cardiac isoforms. Regarding the alternate anaerobic mechanism of ATP production, these differences may explain in part the sex differential susceptibility to hemodynamic compromise in response to cardiovascular stress, in favor of females.
authors.affiliation: Departamento de Bioquímica, CINVESTAV-IPN Av. Instituto Politécnico Nacional No. 2508, México, D.F. 07340. oramirez@mail.cinvestav.mx
authors.forename: O C
authors.initials: OC
authors.lastname: Ramírez
authors.forename: E
authors.initials: E
authors.lastname: Jiménez
mesh_terms: D000818:Animals; D003402:Creatine Kinase / Q000378:metabolism*; D005260:Female; D007527:Isoenzymes / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D051381:Rats; D017208:Rats, Wistar; D012727:Sex Characteristics
chemical_list: D007527:Isoenzymes; D003402:Creatine Kinase