Aim: 

The aim of this study was to find out effects of dexamethasone treatment and exercise on collagen expression in rat cardiac left ventricular wall.

Methods: 

Collagen synthesis was measured as prolyl 4-hydroxylase activity and type I and III collagen mRNA levels. Collagen degradation was studied by measuring mRNA level and quantity of gelatinases. Rats were treated daily with dexamethasone or saline for 3 or 10 days. Eight groups of dexamethasone- treated and control rats were engaged to daily endurance or sprint running exercise. Total duration of endurance running was 60 min within 3 days, and 5 hours 15 min within 10 days. Sprint running consisted of progressively repeated (5–15 times) 30 s spurts to a mild uphill (5°).

Results: 

Three-day dexamethasone treatment decreased type I and III collagen mRNA levels. Ten-day dexamethasone treatment decreased also the activity of prolyl 4- hydroxylase and the quantity of pro-matrix metalloproteinase-2. Exercise by itself did not affect collagen synthesis, but in combination with dexamethasone treatment sprint running prevented most of the dexamethasone-induced reduction in collagen synthesis.

Conclusions: 

Dexamethasone treatment reduced the synthesis and probably also the degradation of collagens in the myocardium. Novel finding was also that sprint running was clearly more effective than endurance running in prevention of these glucocorticoid-induced changes. The high loading of the heart during sprint running possibly requires preservation of the extracellular matrix, which distributes the forces generated by myocardial contractions.