The effect of captopril on renal blood flow in renal artery stenosis assessed by positron tomography with rubidium-82.

Abstract

SUMMARY The sequence and magnitude of acute changes in renal blood flow following administration of captopril were determined in a canine model of acute unilateral renal artery stenosis using rubidium-82 and positron emission tomography. Data were recorded in each of nine dogs under three conditions: 1) during a baseline control interval, 2) during renal artery stenosis, and 3) during stenosis with intravenous injection of captopril (1.2 mg/kg). Mean arterial blood pressure was 108 ± 12 mm Hg at control, increased significantly to 125 ± 13 mm Hg (p<0.01) during stenosis, and decreased to 98 ± 13 mm/Hg (p<0.01) after captopril infusion. Mean renal blood flow was calculated using a steady state single compartment model from the images produced by positron emission tomography. The estimated flow to the affected kidney was 3.37 ± 1.48 ml/min/g at control, 0.86 ± 0.62 ml/min/g during stenosis ( p < 0.01), and 0.64 ± 0.57 ml/min/g after captopril administration (p= NS compared with precaptopril value). The estimated flow to the contralateral kidney was minimally reduced from a baseline of 3.84 ± 0.95 to 3.24 ±1,13 ml/min/g (p=NS) during stenosis and increased after captopril infusion (4.08 ± 0.94 ml/min/g; p = 0.01). These data suggest that repetitive imaging with positron emission tomography can be used to delineate acute changes in renal perfusion following captopril administration. (Hypertension 11: 217-222, 1988).

Renal plasma flow (RPF) measured with multiple-inversion-time arterial spin labeling (ASL) and tracer kinetic analysis: Validation against a dynamic contrast-enhancement method

“…Renal perfusion, often reported as renal plasma flow (RPF), has been shown to be a valuable parameter for assessing renal diseases including chronic kidney disease [1], renal artery stenosis [2], and diabetic nephropathy [3,4]. Para-aminohippurate (PAH) clearance methods for measuring RPF [5,6] involve complicated procedures requiring urine collection and blood sampling [7], and do not measure RPF separately for the individual kidneys.…”

Scintigraphic Imaging of Renal Function

“…For the bolus injection technique, there are two classes of tracer: firstly, so-called ‘chemical’ microspheres, which have a high extraction and retention in tissue [9, 10, 11, 12, 13, 14], and secondly, highly diffusible tracers with perfusion-limited transport between tissue and blood, such as labelled water [14, 15, 16, 17, 18, 19]. The bolus injection approach can be based on either class of tracer but the steady-state technique must use an ultra-short-lived tracer [20, 21, 22, 23]. …”

“…Measurement of tissue perfusion at steady state makes use of ultra-short-lived tracers such as oxygen-15-labelled water [20], which has a half-life of 2 min, and rubidium-82 [21, 22, 23], which has a half-life of 75 s.…”

“…However, for the kidney, λ is only modest and so C τ /C a is a non-linear function of perfusion, as it is for labelled water, and equation 4 needs to be used [22, 23]. Unfortunately, however, λ, like E, is also likely to be inversely dependent on perfusion.…”

“…A significant advantage of PET for measuring renal blood flow is that because the radionuclides are generally short-lived, measurements can be repeated relatively frequently, thereby making it an almost ideal tool for studying physiological interventions in humans, whether using the steady-state technique, which provides a real-time continuous measurement of perfusion, or the bolus injection technique based on oxygen-15 (half-life 2 min) [17, 18], rubidium-82 (75 s) [22, 23], copper-62 (9.7 min), or nitrogen-13 (10 min). Generator-produced radionuclides, such as copper-62 and rubidium-82, can be used remote from a cyclotron in contrast to oxygen-15 for which one must be on-line to the cyclotron.…”