Bo Odlind

Enhanced Local Production of Complement Components in the Small Intestines of Patients with Crohn's Disease

There is evidence that complement components may be formed locally in inflammatory lesions containing monocytes and macrophages. To investigate the role of complement in Crohns disease we measured jejunal-fluid concentrations of the complement components C4, C3, and factor B by perfusion of a closed segment of the jejunum in 22 patients with Crohns disease thought to be limited to the terminal ileum. The mean (+/- SEM) jejunal-fluid C4 concentration was 2.0 +/- 0.3 mg per liter, significantly higher than the mean level in 35 healthy controls (0.7 +/- 0.1 mg per liter; P less than 0.001). The mean C3 concentration was 1.0 +/- 0.1 mg per liter in the patients and 0.7 +/- 0.1 mg per liter in the controls (P less than 0.05). The factor B levels were similar in the two groups. Calculated rates of intestinal secretion of these components showed differences of the same magnitude. Leakage of protein from plasma was not increased. The jejunal-fluid:serum ratios of these complement proteins indicated that their appearance in the lumen of the jejunum was due to at least in part to local mucosal synthesis. The increased jejunal secretion of C4, but not C3 or factor B, paralleled the clinical activity of Crohns disease. Values were normal in first-degree relatives of the patients (n = 13), patients with celiac disease (n = 8), and patients with ulcerative colitis (n = 4). We conclude that increased secretion of complement by clinically unaffected jejunal tissue in patients with Crohns disease reflects the systemic nature of this disorder and may be due to the stimulated synthesis of complement by activated intestinal monocytes and macrophages.

Renal tubular secretion and effects of furosemide

Continuous intravenous infusion of furosemide (8 mg/hr) to 6 healthy subjects induced an average diuresis at steady state of 667 ± 144 ml/30 min (±SD) with a mean plasma concentration of furosemide of 623 ± 209 ng/ml. The urinary output of Cl− was 50.4 ± 7.5, of Na+ 47.7 ± 8.7, and of K+ 5.4 ± 0.6 mmole/30 min. Intravenous injection of probenecid (1 gm) raised the plasma furosemide level to a maximum of 1,584 ± 151 ng/ml. Despite this, the urinary excretion of water, Cl−, Na+, and K+ decreased to 52%, 39%, 39%, and 52%, respectively, of control values. Probenecid greatly reduced the urinary excretion and renal clearance of furosemide. There was no or negative correlation between the plasma levels of furosemide and its diuretic and saluretic effects. The urinary excretion and renal clearance of the diuretic correlated positively with these effects. No effect of probenecid on protein binding of furosemide was detected. The findings show that the diuretic effects of furosemide depend on active tubular secretion of the drug and thus on its tubular fluid concentration.

Challenge with gliadin induces eosinophil and mast cell activation in the jejunum of patients with celiac disease

PURPOSE The aim of this study was to clarify the role of eosinophils and mast cells in the small bowel in celiac disease. PATIENTS AND METHODS Patients with celiac disease (n = 10) were investigated by perfusion of a closed jejunal segment. The concentrations of certain granule constituents from eosinophils, eosinophil cationic protein (ECP), and from mast cells/basophils, histamine, were measured and the jejunal secretion rates of these cellular markers were calculated. RESULTS Compared with findings in healthy control subjects (n = 14), increased secretion rates were observed under basal conditions in patients with histopathologically active celiac disease. Gliadin, administered by perfusion to the jejunal segment, induced a fourfold increase in ECP secretion and a twofold increase of histamine secretion in patients with celiac disease (n = 7), but did not influence the secretion rates of these substances in healthy controls (n = 3). The secretion rate of ECP started to increase 20 minutes after challenge of the perfused segment with gliadin and reached maximum levels 40 minutes later. The secretion rate of histamine started to increase 40 minutes after gliadin administration. Concurrently with these inflammatory events, the secretion of albumin was doubled as a sign of increased mucosal leakage. CONCLUSION These data indicate that eosinophils and mast cells are both involved in the early gliadin-induced reactions of the small intestine, and suggest that these cells are effector cells participating in the celiac lesion of the mucosa.

Extensive tubular secretion and reabsorption of creatinine in humans.

The validity of creatinine as a marker for the glomerular filtration rate was studied in 8 healthy volunteers in different stages of hydration and during large variations in urinary flow rates. The urine flow was 8.4 ml/min in a dehydrated state (due to furosemide infusion; 8 mg/h) and raised to 23.2 ml/min after rapid rehydration. The creatinine to inulin clearance ratio changed considerably from 1.47 in rehydrated state, indicating a substantial tubular secretion of creatinine, to 1.05 in dehydrated state, indicating a reabsorption of creatinine almost equal to secretion. Thus, substantial tubular secretion and reabsorption of creatinine, changing in relative importance in relation to the degree of hydration, make creatinine clearance an unreliable marker for the glomerular filtration rate.

Serum azathioprine and 6-mercaptopurine levels and immunosuppressive activity after azathioprine in uremic patients

The pharmacokinetics of azathioprine (AZA) and 6-mercaptopurine (6-MP) was studied in uremic patients after 100 mg AZA intravenously (fifteen patients) and orally (eight patients). 6-MP was analysed with gas chromatography mass spectrometry following extractive alkylation. AZA was determined indirectly assuming quantitative conversion to 6-MP in whole blood. The plasma concentration of AZA fell rapidly after i.v. administration. The mean half-time of elimination for the first rapid phase (t1/2 alpha) was 6.1 min (S.D. +/- 4.1) and for the terminal phase (t1/2 beta) 50 min (+/- 31). The total plasma clearance (Cl) was 6.9 1./min (+/- 3.0). AZA was rapidly converted to 6-MP in vivo, and maximal plasma concentrations of 6-MP were found as early as 5 min after i.v. injection of AZA. The mean t1/2 alpha was 4.6 min (+/- 2.2), t1/2 beta 74 min (+/- 58) and Cl 8.0 1./min (+/- 5.8). The plasma levels of both AZA and 6-MP were either low or undetectable 4-6 h after dose. In erythrocytes AZA levels were low or undetectable indicating rapid conversion to 6-MP in these cells. 6-MP concentration - time curve in erythrocytes was similar to that in plasma, except for a somewhat slower terminal phase of elimination. Oral administration of AZA generated flat plasma curves for AZA and 6-MP. The area under the concentration - time curve (AUC) was considerably smaller than after i.v. administration, 18 and 41% for AZA and 6-MP, respectively. There seems to be little danger of accumulation of AZA/6-MP in uremia. We also studied inhibition of Leucoagglutin (LA) stimulated lymphocyte proliferation by patient plasma at different times in six of the patients following AZA i.v. Sera drawn at 5, 10 and 30 min significantly inhibited the LA-induced proliferation, with an estimated minimum effective concentration of 6-MP in the cultures of about 0.02-0.04 microM. This suggests the possibility of a therapeutic effect even of the low plasma levels of 6-MP obtained after AZA orally. The combined use of sensitive pharmacokinetic and immunological assays as described should be useful in studying the relationship between plasma levels of AZA/6-MP and their immunosuppressive effect and toxicity.

Delayed tolerance to furosemide diuresis. Influence of angiotensin converting enzyme inhibition by lisinopril.

The role of the renin-angiotensin-aldosterone system in the development of tolerance to the diuretic effect of furosemide was investigated in 12 healthy male volunteers. Furosemide in a dose of 40 mg daily for one week had a brisk acute diuretic effect, but did not lead to dehydration, hyponatremia or fall in blood pressure. The reason for this was a reduction in sodium excretion between doses (rebound effect) and a decrease in sensitivity to furosemide from day 1 to day 7. The latter phenomenon is referred to as delayed tolerance to furosemide. Inhibition of angiotensin converting enzyme with lisinopril 20 mg daily did not change the renal furosemide excretion rate, the renal sensitivity to furosemide or the tolerance development. Thus, delayed tolerance to furosemide diuresis was not related to dehydration or activation of the renin-angiotensin-aldosterone system. Other mechanisms, probably intrarenal, will have to be looked for.

On the Mechanism of Acute Tolerance to Furosemide Diuresis

The renal response to continuous furosemide infusion (8 mg/h) and subsequent ECV changes was studied in 8 healthy volunteers. Furosemide increased urine flow from a basal flow of 4.3 ml/min to a maximum of 15.4 ml/min. During dehydration (-1.8 kg) the diuresis decreased to 8.4 ml/min. The sodium, chloride and potassium excretion likewise decreased. This reduction in diuretic effect (acute tolerance) was accompanied by significantly increased plasma levels of norepinephrine (1.38 to 2.14 nmol/l), PRA (0.52 to 1.13 ng/ml/h) and aldosterone (0.29 to 0.45 nmol/l). After rehydration the urine flow increased to 23.1 ml/min. The changes in diuretic response from initial effect to the dehydrated state and after rehydration were mainly a consequence of changed renal sensitivity to furosemide (urinary excretion of 21 to 14 to 35 mumol Na+ per microgram furosemide excreted). It is proposed that activation of the sympathetic nervous system and/or the renin-angiotensin-aldosterone system may play a role in mediating the acute tolerance to furosemide diuresis. The relative importance of each remains to be clarified.

Extractive alkylation of 6-mercaptopurine and determination in plasma by gas chromatography-mass spectrometry.

An analytical procedure was developed for the determination of 6-mercaptopurine in plasma. Owing to the polar character and low plasma concentration of the compound, extraction and derivatization was carried out directly from the plasma sample by extractive alkylation. Determination was made using gas chromatography-mass spectrometry with multiple-ion detection. Conditions with respect to the rate of formation and the stability of the derivative formed in the extractive alkylation step were evaluated. The selectively of the method to azathioprine and to metabolites was thoroughly investigated. No 6-mercaptopurine was formed from azathioprine added to water or plasma and run through the method. The method enables the detection of 2 ng of 6 mercaptopurine in a 1.0-ml plasma sample. Quantitative determinations were done down to 10 ng/ml 6 mercaptopurine in plasma.

Pharmacokinetics and effects of frusemide in patients with the nephrotic syndrome

SummaryThe renal handling and effects of an intravenous bolus of frusemide with and without plasma volume expansion with dextran or albumin, and with large variations in plasma albumin concentration, have been studied in five patients with the nephrotic syndrome.Decreased renal sensitivity to frusemide was found in only one patient, who also had hypovolaemia and an activated renin-angiotensin-aldosterone system. Plasma volume expansion increased the diuresis but not the saluresis, and slightly increased renal sensitivity to frusemide.An increase in albuminuria after albumin infusion did not reduce the sensitivity to frusemide. A decrease in plasma albumin concentration from 33 g·l−1 after albumin infusion to 23 g·l−1 after infusion of dextran caused a substantial increase in the renal clearance (from 84 to 123 ml·min−1), non-renal clearance (from 72 to 138 ml·min−1), and apparent volume of distribution (from 13 to 23 l) of frusemide, probably as a consequence of an increase in the unbound fraction. The rate of urinary excretion of frusemide was highest after albumin infusion, despite the fact that its renal clearance was lowest then.

Effects of cold ischemia and reperfusion on trapping of erythrocytes in the rat kidney

Abstract. After reperfusion of kidneys subjected to a period of warm ischemia, the medulla displays a vascular congestion of erythrocytes, especially in the inner stripe of the outer zone, a phenomenon referred to as “trapping.” This trapping causes reflow alterations, thus contributing to postperfusion medullary ischemia. The purpose of the present investigation was to study whether trapping also occurs after reperfusion of kidneys following varying periods of cold ischemia and to determine if there is any correlation between the degree of cold ischemic injury and the extent of erythrocyte trapping. Rat kidneys stored at +4°C for 0–30 h were transplanted into recipient animals pretreated with a 51Cr‐labelled erythrocyte suspension. Twenty minutes after reperfusion, the grafts were removed and microdissected into cortex, outer and inner stripes of the outer medullary zone, and inner zone, respectively. The radioactivity of these specimens was measured, and the erythrocyte content for each specimen was calculated. The results show a maximal trapping for cold ischemia time (CIT) of about 12–15 h. A linear correlation between the amount of trapping and CIT could be found in all parts of the kidney (except for the cortex) for CIT 0–15 h. The best correlation was found in the part where the trapping was most prominent, i.e., in the inner stripe. After CIT of 15 h or more, no correlation could be found. It is suggested, as described in models of warm ischemia, that the obstructions of the capillaries by trapped erythrocytes following reperfusion is of pathophysiological significance for the development of post‐transplant acute renal failure. Furthermore, the strong correlation between CIT and the extent of erythrocyte trapping, particularly in the inner stripe, indicates that measurement of erythrocyte trapping after reperfusion could be a sensitive indicator of the degree of cold ischemic damage.