Alterations in collagen metabolism in heart and kidney on dexamethasone administration in rats.

Total collagen content in heart decreased significantly till day 8 of dexamethasone (Dex: 2.5 mg/kg week; s.c. for 2 weeks) treatment and increased on withdrawal of Dex. Acid soluble collagen content in heart decreased till day 12 of Dex treatment, reached normal level on day 16 of Dex treatment and exhibited an increase thereafter. Pepsin solubilized fraction in heart also behaved similarly as the acid soluble fraction, but reached normal level on Dex withdrawal. The total collagen content and the acid soluble collagen in kidney decreased significantly throughout treatment as well as on Dex withdrawal whereas, the pepsin solubilized collagen fraction in kidney exhibited a significant increase from day 8 of Dex treatment and the level was maintained throughout the experiment. Incorporation of 14C-proline in both, heart and kidney was found to be reduced. Electrophoretic pattern of pepsin collagen solubilized fraction of heart and kidney revealed alterations in subunit composition and its types on Dex administration and withdrawal. Thus, administration of Dex induced alterations in the metabolism of collagen and on Dex withdrawal, the system slowly tended to attain normalcy.

Collagen profile in isoproterenol induced myocardial necrosis in rats.

Studies on collagen in heart are important to understand the pathogenesis of myocardial necrosis and to evaluate cardiac function in infarcted heart. The present study has been undertaken to find out the alterations in collagen types in heart as well as serum proteins during myocardial injury in rats. A decreased collagen content was observed on day one which may be due to increased secretion of collagenase and proteases from inflammatory cells or from the myocardium. The changes noticed in the collagen types (I, III and V) indicated the altered elasticity of the heart. Histological studies were observed to correlate well with the biochemical changes in collagen. Evaluation of myocardial collagen could provide new approaches to the treatment of infarct size reduction.

Collagen levels in isoproterenol induced myocardial infarction in rats.

Myocardial infarction was induced in albino rats by the subcutaneous administration of isoproterenol. A significant was observed increase in weight of the myocardium, total protein, DNA levels, neutral salt soluble collagen content, serum and urinary hydroxyproline levels at peak infarction stage in treated rats while the body weight, insoluble and total collagen content of heart were found to be decreased. These results show an early degradation of collagen immediately after myocardial infarction and enhanced synthesis during the different stages of recovery. Histological studies confirmed the incidence of peak infarction after two doses of isoproterenol treatment and recovery to normalcy from the third day onwards.