ISSN:
1435-1803
Keywords:
exercise
;
fasting
;
isoenzymes
;
myosin
;
SHR
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary A statistical model is presented which describes quantitatively the distribution of ventricular myosin (VM) isoenzymes VM-1, VM-2 and VM-3. In order to account for the actual distribution of the isoenzymes, it was assumed that the probability for formation of the heterodimer VM-2 (alpha- and beta-heavy chain) is lower than that of the homodimers VM-1 (2 alpha-heavy chains) or VM-3 (2 beta-heavy chains). The relation VM-2=0.85 (VM-1·VM-3)0.5 describes quantitatively the proportion of the 3 isoenzymes in a given population. The model was established for 252 sedentary normotensive Wistar rats and spontaneously hypertensive rats (SHR) fed ad libitum. It is demonstrated that the isoenzyme populations of rats subjected to 8 weeks experimental routines involving intermittent feeding (1 day feeding ad libitum, followed by 1 or 2 days fasting) or swimming also obey this theoretical distribution. Intermittent feeding led to an increased proportion of VM-3 in Wistar rats and SHR, whereby the latter approached the limits of the possible distribution. Intermittent swimming resulted in an increased proportion of VM-1 which was independent of the feeding schedule in SHR. In Wistar rats, however, the swimming rats fed intermittently exhibited a significantly smaller proportion of VM-1. By combining certain experimental routines, it is thus possible to induce within 8 weeks an isoenzyme population of a predefined composition, nearly within the whole range of possible distribution. The data further demonstrate that the formal correlation between the proportion of beta-heavy chains in a myosin population and ventricular mass holds only when the rats are kept under standard conditions. Following the routines involving an altered pattern of food intake or intense physical activity, the isoenzyme population can be altered in a manner unrelated to ventricular mass. Thus, swimming induced a redistribution in favour of VM-1 irrespective of the feeding pattern, although ventricular mass differed greatly in both the intermittently or ad libitum fed swimming rats. It is concluded that, besides ventricular mass, neuro-endocrine status is decisive for the isoenzyme population of myosin.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01907859
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