HEART PROLYL ENDOPEPTIDASE ACTIVITY IN ONE-KIDNEY, ONE-CLIP HYPERTENSIVE RATS

1. Heart mass, prolyl endopeptidase activity and fractionated proteins from heart tissue were studied in one-kidney, one clip hypertensive r ats (N = 6) and compared to sham-operated rats (N = 6). 2. Body weight , arterial pressure and tissue mass were measured 4 weeks after artery clipping. Z-Gly-Pro-p-nitroaniline hydrolysis was used to measure tis sue prolyl endopeptidase activity in the homogenate. Protein was fract ionated into the soluble and myofibrillar fractions. 3. In the normote nsive rats, prolyl endopeptidase activity expressed in terms of protei n specific activity (mu M substrate hydrolyzed h(-1) mg supernatant pr otein(-1)) occurred in atria and was 2.5-fold higher than in the ventr icles (3.79 +/- 0.20 vs 1.44 +/- 0.02, P<0.05). In the one-kidney, one clip hypertensive rats, the left ventricle tissue increased 1.7-fold (2.27 +/- 0.11 vs 3.72 +/- 0.11 mg wet weight tissue/g body weight, P< 0.001), the soluble protein fraction (54.86 +/- 3.60 vs 57.38 +/- 6.64 mg/g wet weight tissue) was unchanged, while the myofibrillar fractio n increased 1.9-fold (118.9 +/- 9.09 vs 229.8 +/- 8.47 mg/g wet weight tissue, P<0.001). 4. The specific activity of the atrial and ventricu lar prolyl endopeptidase decreased in atria and increased in ventricle s as the result of hypertension (3.79 +/- 0.2 vs 2.84 +/- 0.13 and 1.4 4 +/- 0.02 vs 1.87 +/- 0.13; respectively). These regional differences in prolyl endopeptidase enzyme content caused by one-kidney, one clip hypertension in neurosecretory and non-neurosecretory heart areas sug gest that this enzyme plays a local role in the turnover of specific p olypeptides.