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Extrarenal angiotensin-forming enzymes
Summary
Tonin, a serine protease, directly forms angiotensin II. Its characteristics, presence in rat kidney distal tubules and urine, and influence on blood pressure regulation are detailed.
Area of Science:
- Biochemistry
- Physiology
- Enzymology
Background:
- Enzymes facilitate angiotensin formation in tissues.
- Two pathways exist: angiotensin I formation (renin, cathepsin D) and direct angiotensin II formation (cathepsin G, tonin).
- Tonin's role in the renin-angiotensin system requires further elucidation.
Purpose of the Study:
- To characterize tonin, a serine protease involved in direct angiotensin II formation.
- To investigate tonin's presence and function in rat kidney and urine.
- To explore tonin's potential role in hypertension.
Main Methods:
- Amino acid sequencing to determine 80% of tonin's sequence.
- Comparative analysis of tonin with other proteases (serine proteases, renin, cathepsin D, ACE).
- In vivo studies in 1K-1C hypertensive rats and analysis of tonin in rat kidney and urine samples.
Main Results:
- 80% of tonin's amino acid sequence was determined.
- Tonin exhibits distinct characteristics compared to other serine proteases, renin, cathepsin D, and angiotensin I converting enzyme.
- Tonin was found in rat kidney distal tubular cells and in urine, with excretion influenced by age and sodium intake.
Conclusions:
- Tonin is a unique serine protease directly involved in angiotensin II formation.
- Tonin is present in the rat kidney and its urinary excretion is modulated by physiological factors.
- Further research into tonin's role in blood pressure regulation and hypertension is warranted.