Angiotensin I-converting enzyme activity in tubular fluid along the rat nephron

Angiotensin I-converting enzyme activity in tubular fluid along the rat nephron

Author Casarini, Dulce Elena Autor UNIFESP Google Scholar
Boim, Mirian Aparecida Autor UNIFESP Google Scholar
Stella, Regina Celes de Rosa Autor UNIFESP Google Scholar
Krieger-Azzolini, M. H. Autor UNIFESP Google Scholar
Krieger, Jose Eduardo Autor UNIFESP Google Scholar
Schor, Nestor Autor UNIFESP Google Scholar
Institution Universidade Federal de São Paulo (UNIFESP)
Universidade de São Paulo (USP)
Abstract The activity of angiotensin I-converting enzyme (ACE) was determined in tubular fluid collected from several portions of the rat nephron and urine and in total and efferent arteriolar blood using hippuryl-L-His-leu as substrate. ACE activity decreased 30% from the pre- to the postglomerular arterioles (P < 0.001), suggesting a role of the glomerulus in ACE clearance. The enzyme activity was found to be present throughout the rat nephron. However, the highest activities were found in the proximal tubule and urine (0.692 +/- 0.007 and 1.05 +/- 0.015 pmol .mu l(-1). min(-1), respectively). Compared with other segments, ACE activity decreased from the initial portion of the proximal tubule to the distal nephron and increased again in the urine. Along the proximal tubule, ACE was secreted and degraded and/or reabsorbed and then secreted again into the collecting duct; no ACE activity was found in the late distal tubule, but a high level was detected in the urine, indicating a potential physiological role in the inactivation of the kinins formed by kallikrein beyond the connecting tubules. Moreover, the possible role of mesangial cells (MC) in the decrease of intraglomerular ACE was also evaluated. The analysis of ACE gene showed that MC in culture are able to express ACE mRNA. Moreover, ACE is produced as an ectoenzyme and as a secreted form of the enzyme, indicating a potential effect of local angiotensin II production on MC function.
Keywords micropuncture
tubular fluid
mesangial cells
kininase II
Language English
Date 1997-03-01
Published in American Journal Of Physiology-renal Physiology. Bethesda: Amer Physiological Soc, v. 272, n. 3, p. F405-F409, 1997.
ISSN 1931-857X (Sherpa/Romeo, impact factor)
Publisher Amer Physiological Soc
Extent F405-F409
Access rights Closed access
Type Article
Web of Science ID WOS:A1997WP85000017

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