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Heart prolyl endopeptidase activity in one-kidney, one clip hypertensive rats
M A Cicilini1, P S Ramos, E C Vasquez
1Departamento de Ciências Fisiológicas, Universidade Federal do Espírito Santo, Vitória, Brasil.
Insights
Hypertension altered prolyl endopeptidase activity in rat hearts, decreasing it in atria and increasing it in ventricles. This suggests the enzyme plays a local role in polypeptide turnover within specific heart regions.
Area of Science:
- Cardiovascular Physiology
- Enzymology
- Hypertension Research
Background:
- Prolyl endopeptidase (PEP) is an enzyme involved in protein processing.
- Hypertension is associated with significant cardiac remodeling and altered protein metabolism.
Purpose of the Study:
- To investigate the impact of one-kidney, one clip hypertension on heart mass, prolyl endopeptidase activity, and protein fractions.
- To determine regional differences in prolyl endopeptidase activity within the hypertensive rat heart.
Main Methods:
- One-kidney, one clip hypertension model in rats (N=6) compared to sham-operated controls (N=6).
- Measurement of body weight, arterial pressure, and heart tissue mass 4 weeks post-surgery.
- Assay of prolyl endopeptidase activity using Z-Gly-Pro-p-nitroaniline hydrolysis.
- Fractionation of heart proteins into soluble and myofibrillar components.
Main Results:
- Hypertensive rats showed a 1.7-fold increase in left ventricle mass and a 1.9-fold increase in myofibrillar protein fraction.
- Prolyl endopeptidase specific activity decreased in atrial tissue (3.79 to 2.84) and increased in ventricular tissue (1.44 to 1.87) in hypertensive rats.
- Soluble protein fraction remained unchanged in hypertensive rats.
Conclusions:
- One-kidney, one clip hypertension induces significant cardiac structural changes, including left ventricular hypertrophy and altered myofibrillar protein content.
- Hypertension leads to a redistribution of prolyl endopeptidase activity within the heart, with decreased activity in atria and increased activity in ventricles.
- These enzyme activity changes suggest a localized role for prolyl endopeptidase in regulating polypeptide turnover in specific cardiac regions during hypertension.
Abstract:
1. Heart mass, prolyl endopeptidase activity and fractionated proteins from heart tissue were studied in one-kidney, one clip hypertensive rats (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 tissue prolyl endopeptidase activity in the homogenate. Protein was fractionated into the soluble and myofibrillar fractions. 3. In the normotensive rats, prolyl endopeptidase activity expressed in terms of protein specific activity (microM substrate hydrolyzed h-1 mg supernatant protein-1) occurred in atria and was 2.5-fold higher than in the ventricles (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 fraction 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 ventricular prolyl endopeptidase decreased in atria and increased in ventricles as the result of hypertension (3.79 +/- 0.2 vs 2.84 +/- 0.13 and 1.44 +/- 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 suggest that this enzyme plays a local role in the turnover of specific polypeptides.