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Summary Cardiomyopathy was produced by isoprenaline injections to healthy and hydrazinophthalazine-treated rats. The activity of leukocyte collagenase and collagenolytic cathepsin was determined on the 2nd, 7th, 19th and 21st day after the last isoprenaline injection. At the same time morphological studies of the heart muscles were carried out. It was found that alterations in enzyme activity were different in healthy and hydrazinophthalazine-treated rats. A negative synergism of isoprenaline as regards the hydrazinophthalazine action was observed in biochemical and morphological studies.

Summary Hydralazine (1-hydrazinophthalazine) was administered in drinking water as a 0.0312% solution to randomly bred Swiss mice for life beginning at 5 weeks of age. The treatments gave rise to statistically significant incidences of lung tumors: 55% in females and 43% in males. A decreased copper concentration and superoxide dismutase activity in the lung of mice were observed. The role of copper and superoxide dismutase in the malignant process is briefly discussed.

Collagen-like syndrome was induced in rats by oral hydralazine administration during 5 months. After 4 months, a subgroup of rats was shifted from the standard diet to the diet supplemented with copper (II) (60 micrograms of copper per g of pellet) as copper sulphate. A decreased serum copper concentration was noted, LE cells were observed in the blood of 75% of rats fed with standard diet. In the subgroup of copper supplemented rats, the LE cells were observed in 40% of rats only. The activity of superoxide dismutase, the antioxidative copper-dependent enzyme, was significantly lower in erythrocytes of rats fed with standard diet, than the activity in rats fed with copper supplemented diet. These results are briefly discussed.

In this study, we sought to determine the role of neutral proteases in cartilage matrix proteoglycan degradation, which occurs during the experimental hydralazine-induced collagen-like syndrome (c-l-s) in rats. The digestion of endogenous proteoglycans by neutral proteases in homogenates of cartilage from rats with c-l-s has been measured and compared with that of normal age-matched controls. Cartilage specimens from the tibial plateau were analysed for DNA and proteoglycan content, and neutral proteoglycan-degrading activity, No significant difference in cartilage DNA concentration was observed among the rats with c-l-s and the controls. Total neutral proteoglycan-degrading metallo-enzyme activity, determined by direct tissue assay, was significantly higher in c-l-s cartilage than that in control cartilage. Serine protease activity on proteoglycans was much lower than that of metalloprotease. The results of this study are consistent with the hypothesis that the neutral metalloproteases of cartilage are involved in the degradation of proteoglycans in c-l-s.