A simple technique for estimating glomerular filtration rate with subcutaneous injection of (125I)lothalamate.
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Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were simultaneously measured by obtaining an isotopic steady state during a continuous infusion of 125I orthoiodohippurate (OIHA). A good correlation was found between the clearances of Ioth (y) and of inulin or polyfructosan (x) : y = 1.18 X (x) + 8.43 (r = 0.96; P less than 0.001) and between the clearances of OIHA (y') and of PAH (x') : y' = 0.62 X (x') + 21.2 (r = 0.93; P less than 0.001). When renal functions were impaired the use of Ioth was not convenient since the infusion time necessary to reach a radioactive plateau was longer than 3 hours. On the contrary, excellent results were obtained by using OIHA. In this case, the main advantages were the absence of urine collection and the rapid obtention of an isotopic equilibrium. The repeated determination of renal clearances in hypertensive or diabetic patients appears to be useful in the study of changes induced by antihypertensive drugs or insulin. Clearances were slightly improved by clonidine, claimed to be useful in hypertension associated with chronic renal failure. GFR and ERPF were rapidly increased by insure on the metabolic and hemodynamic changes induced by insulin than on the return to normal of glomerular basement membrane permeability.
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Intravenous (i.v.) infusion of the selective vasopressin (V2) agonist 1-desamino-8-D-arginine vasopressin (DDAVP, Desmopressin) in humans causes a fall in blood pressure, an increase in heart rate, and a rise in plasma renin and noradrenaline. The present study was designed to demonstrate the vasodilatory properties of DDAVP in the renal circulation and to describe the effect of DDAVP on renin secretion. Seven male subjects (31-63 years) with hypertension, who showed no signs of renal parenchymal disease, received an i.v. infusion of DDAVP (400 ng/kg in 10 minutes). They were studied at the time they were undergoing renal vein renin sampling and renal angiography as part of the diagnostic work-up of their hypertension. 131I-Hippurate clearance was used to measure effective renal plasma flow (ERPF). True renal plasma flow was calculated as ERPF divided by the renal extraction ratio of 131I-hippurate. 125I-Thalamate clearance was used to measure glomerular filtration rate (GFR). Measurements were made before and 15-20 minutes after administration of DDAVP. Angiography was performed in the same session after the last blood samples had been collected. In all patients the renal arteries were normal and the extraction ratios of 131I-hippurate and 125I-thalamate (Ehip, Ethal) were not different for the left and right kidney, and in all seven patients a diagnosis of essential hypertension was made. After DDAVP systolic blood pressure decreased by 14.4 mmHg (2.0-26.8) (mean, 95% confidence interval, p < 0.05). Diastolic blood pressure decreased by 12.1 mmHg (2.9-21.7, p < 0.01). Heart rate increased by 17.5 bpm (11.7-23.2, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
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A simple high-performance liquid chromatographic (HPLC) method was developed for the simultaneous determination of iohexol, iothalamate, p-aminohippuric acid (PAH) and n-acetyl-p-aminohippuric acid (n-acetyl-PAH) in human plasma and urine. A C(18) column at a flow rate of 1 ml/min with an aqueous mobile phase of trifluoroacetic acid (0.1% TFA in deionized water (pH 2.2), v/v) and methanol gradient was used for component separation. The plasma and urine assay demonstrated linearity from 10 to 50 microg/ml for iohexol and iothalamate, 5 to 40 microg/ml for PAH and 2.5 to 40 microg/ml for n-acetyl-PAH. The HPLC plasma and urine results obtained for PAH were used to calculate the subject kidney effective renal plasma flow (ERPF) and the iohexol results were used to calculate the subject kidney glomerular filtration rate (GFR). The HPLC results for PAH were then compared to an alternative colorimetric method for analyzing PAH to determine if subject metabolism (acetylation) of PAH affected the ERPF results obtained using the colorimetric method, the subsequent ERPF/GFR ratio and clinical impression of subject patient kidney function. The method was utilized in several different clinical studies evaluating the effect of kidney function from medications (phase IV evaluations) marketed for patients with cardiovascular disease.
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