Group Process and Organizational Environment: Student Organizations in the University

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68768/2/10.1177_089976407400300305.pd

In vitro production of angiotensin II by isolated glomeruli

The glomerulus has several components of the renin-angiotensin system (RAS). The purpose of this study was to evaluate the ability of glomeruli isolated from adult Wistar-Kyoto rats to produce angiotensin II (ANG II). When isolated glomeruli were incubated in Krebs buffer, the peak concentration of immunoreactive angiotensin (ANG) in the incubation medium, representing simultaneous production and degradation, occurred after 15 min of incubation (3.98 +/- 0.34 pg.mg protein-1.15 min-1, of which 18% was ANG II. When 125I-labeled ANG II was incubated with isolated glomeruli, the half-life of ANG II was 6.06 min. Hence, we estimated ANG II production at 3.77 +/- 0.21 pg.mg protein-1.15 min-1. When angiotensinogen-rich serum was added to the incubation medium, ANG concentration at 15 min increased by 500-fold (1,978 +/- 44 pg.mg protein-1.15 min-1, P &lt; 0.001). ANG concentration in the glomerular incubate responded to perturbations known to alter systemic RAS. Enalaprilat, chymostatin, propranolol, and renin antiserum decreased ANG concentration in glomerular incubate, whereas salt depletion increased this (P &lt; 0.05). We conclude that the rat glomerulus can generate ANG II independent of neural, hormonal, or vascular control. </jats:p

Endogenous angiotensin concentrations in specific intrarenal fluid compartments of the rat.

To examine angiotensin (ANG) concentrations in fluid compartments near known intrarenal ANG receptors, we measured ANG concentrations in glomerular filtrate (GF), star vessel plasma (SVP), and luminal fluid from the early, mid, and late proximal tubule (E, M, and L PT). Samples were collected from euvolemic Munich-Wistar rats by free-flow micropuncture; ANG concentrations were measured by RIA. In one group of rats, concentrations of total immunoreactive ANG (reflecting ANG II and lesser amounts of three fragments) in GF and E, M, and L PT fluid averaged 29-40 nM compared with 32 pM in systemic plasma. In a second group, immunoreactive ANG concentrations in SVP also exceeded systemic levels by a factor of 1,000. In a final group, samples of GF and LPT fluid were purified by HPLC before RIA to measure ANG II and III concentrations specifically: their respective concentrations were 6-8 nM and 14-25 nM. We interpret these results to indicate that substantial amounts of ANG peptides are released into or generated within intrarenal fluid compartments, in which local ANG is likely to effect regulation of renal function independently of systemic ANG