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Conventional creatinine clearance studies in the pig are complicated by difficulties with catheterisation, infection, accurate collection and active creatinine renal tubular reabsorption. We compared a single injection, 99mTc-DTPA elimination method with creatinine clearance. Nineteen pairs of GFR estimations were performed in 10 pigs: 7 in normal pigs and 12 following bile duct ligation and/or nephrectomy. Red cell and plasma protein binding of the isotope and its hepatobiliary excretion was assessed. Absolute and weight normalised endogenous creatinine clearances correlated significantly with 99mTc-DTPA elimination. 99mTc-DTPA red cell binding and hepatobiliary excretion were negligible. Thus, 99mTc-DTPA elimination is a valid indicator of changes in renal function in grouped porcine studies, particularly in the biliary obstruction model. However, isotope plasma protein binding was high in the 2 normal pigs assessed. Individual accuracy would be improved by routine protein binding correction, unless consistently low for a particular preparation.
Conventional creatinine clearance studies in the pig are complicated by difficulties with catheterisation, infection, accurate collection and active creatinine renal tubular reabsorption. We compared a single injection, 99mTc-DTPA elimination method with creatinine clearance. Nineteen pairs of GFR estimations were performed in 10 pigs: 7 in normal pigs and 12 following bile duct ligation and/or nephrectomy. Red cell and plasma protein binding of the isotope and its hepatobiliary excretion was assessed. Absolute and weight normalised endogenous creatinine clearances correlated significantly with 99mTc-DTPA elimination. 99mTc-DTPA red cell binding and hepatobiliary excretion were negligible. Thus, 99mTc-DTPA elimination is a valid indicator of changes in renal function in grouped porcine studies, particularly in the biliary obstruction model. However, isotope plasma protein binding was high in the 2 normal pigs assessed. Individual accuracy would be improved by routine protein binding correction, unless consistently low for a particular preparation.
Renal cortical microcirculation and its relation to inulin clearance, central haemodynamics and pulmonary gas exchange were studied in eight pigs under continuous intravenous chlormethiazole-pancuronium anaesthesia. The animals were studied during six consecutive 30-min periods. Four of the animals were also studied 19 h after the first period. In the superficial renal cortex, regional blood flow (Qsrc) was measured by laser Doppler flowmetry (LDF) and tissue oxygenation (PtO2) by surface microelectrode technique. Central haemodynamics and pulmonary gas exchange values were distributed within normal ranges. The importance of stable central haemodynamics in order to perform accurate microcirculatory measurements in the renal cortex was documented. A significant relation between Qsrc and pulmonary capillary wedge pressure (PCWP) was found (P less than 0.0001) despite the fact that PCWP was distributed within a range of only 0.7 kPa (all values were well within the normal range for pigs). No other relationships were found between central haemodynamics or pulmonary gas exchange variables and renal microcirculatory parameters. Concerning renal microcirculation and inulin clearance, at least 2-3 h may be required for stabilization after surgery. The average temporal variability between measurements performed every 30 min in each animal was 6 +/- 7% (s.d.) in the LDF values and 21 +/- 21% in the PtO2 values (mean PtO2). No correlations were found between Qsrc or PtO2 and inulin clearance. Since the haemodynamic parameters, pulmonary gas exchange variables and haematocrit were distributed within narrow ranges, we regard the temporal microcirculatory variability obtained here as normal in this experimental situation, and consider the porcine model well suited for further studies concerning renal microcirculation.
Light‐microscopic examinations were performed in three groups of pigs: one sham‐operated control group, one group subjected to thyroidectomy (TX), and one group injected with parathormone (PTH) after thyroidectomy (TX + PTH). The kidneys of the sham‐operated animals were normal, whereas slight to moderate dilatation of some tubules was seen in the TX group. The most prominent changes in the TX + PTH group were calcium deposition, tubular dilatation and degeneration, inflammation, and hyperaemia. In addition there were hyaline casts, PAS‐positive globules and mitotic figures in the tubules. It is suggested that the calcium deposition caused by the PTH administration plays a major role in the development of degeneration in the tubular epithelium, and that these structural lesions are of importance in the development of reduced renal function.
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