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Characterization of angiotensin II formation in human isolated bladder by selective inhibitors of ACE and human chymase: a functional and biochemical study
Author(s) -
Waldec Kristian,
Fredrik Lindberg B,
Persson Katarina,
Andersson KarlErik
Publication year - 1997
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0701240
Subject(s) - enalaprilat , chemistry , chymase , endocrinology , angiotensin converting enzyme , medicine , renin–angiotensin system , angiotensin ii , ace inhibitor , enzyme inhibitor , enzyme , biochemistry , biology , receptor , blood pressure
Functional recordings of smooth muscle tension and biochemical experiments on membrane fractions were performed to characterize angiotensin II (AII) formation in human isolated bladder smooth muscle. A novel human chymase inhibitor CH 5450 (Z‐Ile‐Glu‐Pro‐Phe‐CO 2 Me) and a recently developed human chymase substrate Pro 11 ‐, d ‐Ala 12 )‐angiotensin I, claimed to be resistant to angiotensin converting enzyme (ACE) and carboxypeptidase, were used. Angiotensin I (AI) (0.3μ m ) induced a contractile response amounting to 58±5% ( n =12) of the initial K + (124m m )‐induced contractions. This response was reduced to 36±3% ( n =8) by the ACE‐inhibitor enalaprilat (10μ m ), while pretreatment with soybean trypsin inhibitor (STI 200μg ml −1 ) or CH 5450 (10μ m ) had no effect. However, the combination of enalaprilat and STI reduced the AI‐induced contractions to 19±5% ( n =6), and the combination of enalaprilat and CH 5450 caused an almost complete inhibition of the AI‐induced contractions to 1±1% ( n =6). The substrate (Pro 11 ‐, d ‐Ala 12 )‐AI (3μ m ) produced contractions which amounted to 57±4% ( n =13) of the initial K + (124m m ) contractions. These contractions were not affected by enalaprilat (10μ m ). On the other hand, STI (200μgml −1 ) and CH 5450 (10μ m ) added separately, depressed the (Pro 11 ‐, d ‐Ala 12 )‐AI‐induced contractions to 34±5% ( n =6) and 24±4% ( n =6), respectively. The combination of enalaprilat and STI or enalaprilat and CH 5450 did not produce any further inhibition. Experiments with detrusor membrane fractions incubated with AI (50μ m ) were performed. In the presence of enalaprilat (100μ m ), carboxypeptidase inhibitor CPI (10μgml −1 ) and aprotinin (15μ m ), CH 5450 (10n m –1μ m ) caused a concentration‐dependent inhibition of AII formation. The results confirm that AII is a potent contractile agent in the human isolated detrusor muscle. They also indicate that the serine protease responsible for AII formation in the human bladder in vitro is human chymase or an enzyme similar to human chymase.