5'-Nucleotidase and adenosine deaminase activities in hypertrophied rat heart. The effect of tachycardia.

: Activity of 5'-nucleotidase (5NT) and adenosine deaminase (ADA) in the left heart ventricle was examined at normal heart rate and after atrial pacing in six weeks after constriction of the aorta above or below the renal vessels and in sham operated rats. The aorta constriction above the vessels reduced activity of 5NT by 29% and increased activity of ADA by 33%, whereas the constriction below the vessels resulted in elevated activity of both enzymes: 5NT by 16% and ADA by 145% at normal heart rate. The atrial pacing reduced 5NT activity and did not affect ADA activity in control rats and in those with constriction of the aorta below the vessels. The activity of both enzymes increased after constriction of the aorta above the renal vessels. It is concluded that adenosine metabolism in the hypertrophied heart may be changed due to changes in its production and degradation. Renin-angiotensin-aldosterone system seems to be involved in regulation of the activities of adenosine metabolizing enzymes in the hypertrophied heart.