K.E. Britton

Obstructive nephropathy: successful evaluation with radionuclides.

A non-invasive test of nephron function, the renal parenchymal transit time (P.T.T.) index, is shown to be as accurate as antegrade pressure measurements in diagnosis of renal outflow obstruction. It is more sensitive than conventional methods of demonstrating the associated obstructive nephropathy. P.T.T. is useful in following the effects of surgery, or of temporising, in patients with confirmed or potential outflow tract obstruction. Renal radionuclide P.T.T. analysis gives the functional information essential for the management of patients in whom intravenous urography reveals a dilated renal pelvis.

ESSENTIAL HYPERTENSION: A DISORDER OF CORTICAL NEPHRON CONTROL?

Abstract Intrarenal plasma-flow distribution has been determined non-invasively in man. The reduction in effective renal plasma flow in essential hypertension is due to a reduction in flow to the cortical nephrons only; the juxtamedullary nephrons maintain their flow. A disorder of the autoregulatory control of cortical-nephron flow is postulated to be the genetic defect in essential hypertension.

Clinical evaluation of 99mTc diaminocyclohexane, a renal tubular agent with cationic transport : results in healthy human volunteers

As alternatives to anionically transported hippuran, structure distribution experiments on a series of 99mTc-labelled primary substituted ethylene diamine compounds led to selection of 99mTc diaminocyclohexane (DACH) for clinical evaluation, 99mTc DACH, a cation with the structure trans-[O2(DACH)2 99mTc]+ is prepared by mixing 50 mumol DACH, 1 mumol stannous tartrate and 500 MBq of 99mTc. Seven normal volunteers underwent renal imaging and clearance studies using 150 MBq of 99mTc DACH and 1 MBq of 125I hippuran simultaneously. The images with 99mTc DACH revealed good uptake and excretion. The mean +/- 2 SD values of parenchymal and whole-kidney transit time indices and mean parenchymal transit time were 46 +/- 33, 75 +/- 64 and 141 +/- 51 s, respectively, similar to mercaptoacetyl triglycine. The mean clearance of 99mTc DACH was found to be 163 ml/min (SD = 32). Following cationic blockade with 900 mg oral thiamine, significant reduction (p < 0.001) in DACH clearance was noted, but hippuran clearance remained unaltered. The results support the hypothesis that 99mTc DACH is transported cationically.

Total and Intrarenal Flow Distribution in Healthy Subjects: Technique, Acute Effects of Ibopamine and of Indoramin

A technique is described for measuring an index of cardiac output, total and individual renal plasma flow, cortical and juxtamedullary nephron flow non-invasively in man with a single injection of 123I-o-iodohippurate. Ibopamine, a dopamine analogue, was administered orally, 200 and 600 mg, in a double-blind, placebo-controlled cross-over study in 6 healthy subjects. No change in pulse, blood pressure, cardiac output, urea, creatinine or electrolytes was seen. Ibopamine reduced effective renal plasma flow and cortical nephron flow and increased urine flow significantly. This may be due to differential vasoconstrictor and vasodilator effects on the two populations of nephrons. Indoramin, and alpha-1 postsynaptic adrenoceptor blocker, was administered orally, 50 mg, in a double-blind, placebo-controlled cross-over study in 14 healthy young males. No change in pulse, cardiac output, urea, creatinine or electrolytes was seen. Indoramin significantly reduced upright but not supine blood pressure and significantly increased effective renal plasma flow. Cortical nephron flow and juxtamedullary nephron flow tended to rise. Plasma renin activity was significantly elevated although there was no change in urinary sodium output. The effect of drugs on intrarenal blood flow distribution may be relevant to the management of essential hypertension.

The effect of ramipril. A new angiotensin-converting enzyme inhibitor on cortical nephron flow and effective renal plasma flow in patients with essential hypertension

A placebo-controlled study of Ramipril on total and intrarenal flow distribution was carried out in 7 patients with essential hypertension. Cortical nephron flow was measured using radiolabelled tubular secreted radiopharmaceuticals 123I orthoidohippurate or 99mTc mercaptoacetyl triglycine by the transit time distribution technique. Both systolic and diastolic blood pressure were reduced significantly by Ramipril without significant changes in an index of cardiac output or in effective renal plasma flow. Cortical nephron flow increased from 207 +/- 7 to 257 +/- 21 ml/min (mean +/- SEM) p less than 0.05 and the percentage of flow to cortical nephrons increased by 6% (p = 0.05). Ramipril corrects the reduced cortical nephron flow found in essential hypertension.