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 < 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 < 0.05). We conclude that the rat glomerulus can generate ANG II independent of neural, hormonal, or vascular control.