Mats Sjöquist

Lowering of tumor interstitial fluid pressure specifically augments efficacy of chemotherapy

Chemotherapy of solid tumors is presently largely ineffective at dosage levels that are compatible with survival of the patient. Here, it is argued that a condition of raised interstitial fluid pressure (IFP) that can be observed in many tumors is a major factor in preventing optimal access of systemically administered chemotherapeutic agents. Using prostaglandin E1‐methyl ester (PGE1), which is known transiently to reduce IFP, it was shown that 5‐fluorouracil (5‐FU) caused significant growth inhibition on two experimental tumors in rats but only after administration of PGE1. Furthermore, timing experiments showed that only in the period in which IFP is reduced did 5‐FU have an antitumor effect. These experiments uniquely demonstrate a clear and, according to the starting hypothesis, logical, synergistic effect of PGE1 and 5‐FU that offers hope for better treatment of many tumors in which raised IFP is likely to be inhibiting optimal results with water‐soluble cancer chemotherapeutic agents.

Overexpression of Semicarbazide-Sensitive Amine Oxidase in Smooth Muscle Cells Leads to an Abnormal Structure of the Aortic Elastic Laminas

Elevated semicarbazide-sensitive amine oxidase (SSAO) activity has been observed in several human conditions, eg, diabetes, and it has been speculated that SSAO contributes to the development of vasculopathies associated with this disease. To investigate in vivo consequences of elevated expression of SSAO in vascular tissues, we have developed a transgenic model for overexpression of human SSAO in mice. A smooth muscle-specific promoter, smooth muscle alpha-actin promoter 8 (SMP8) was used. Transgenic expression of human SSAO in tissues with a high content of smooth muscle cells was confirmed by Northern blot analysis. Enzymatic analysis of homogenates from transgenic tissues showed elevated levels of SSAO activity compared to non-transgenic littermates. Furthermore, when plasma SSAO activity was analyzed, much higher activity was detected compared to plasma from control mice, indicating that plasma SSAO may originate from smooth muscle cells. Histopathological evaluation of aorta and renal artery from transgenic mice revealed an abnormal structure of the elastin tissue. Instead of the regularly folded elastic laminae normally found in tunica media of sacrificed mice, the elastic laminae were straight and unfolded with irregularly arranged elastic fibers, forming tangled webs, between the intercalating elastic laminae. These alterations of the elastin structures suggest that overexpression of SSAO has led to a reduced elasticity of the arteries. Moreover, the mean femoral arterial pressure of the SMP8 SSAO transgenic mice was significantly lower in comparison to non-transgenic littermates. This suggests that the transgenic mice have a defect in their ability to regulate blood pressure.

Lowering of tumoral interstitial fluid pressure by prostaglandin E1 is paralleled by an increased uptake of 51Cr-EDTA

High intra‐tumoral fluid pressure (TPIF) may impair uptake of anticancer drugs into tumors, contributing to poor efficiency in treatment of carcinomas. Here, we demonstrate that lowering of TPIF parallels increased transport of 51Cr‐EDTA (m.w. 341) into tumor interstitium. Introduction of 15 μg prostaglandin E1 (PGE1) ‐methyl ester into the s.c. tissue surrounding transplanted rat colonic (PROb) carcinomas or chemically‐induced rat mammary carcinomas, lowered TPIF by 30%. Transcapillary transport into the interstitium of PROb tumors quantified by microdialysis increased by 39.6% after PGE1 treatment 40 min prior to administration of 51Cr‐EDTA (n=6; p<0.05) compared to vehicle (n=10). In mammary tumors, PGE1 increased transport into the tumors by 86.9% over controls (n=16; p<0.05). Both tumors had well developed stroma containing collagen and hyaluronan. Our data demonstrate that adjuvant treatment with PGE1 lowers TPIF, and enhances transport into the tumors. This principle may be of value as adjuvant therapy in treatment of solid malignancies with currently used anticancer drugs. Int. J. Cancer 86:636–643, 2000.

Functional evaluation of cerebral microembolization in the rat

This study investigates the effects of cerebral microembolism on motor performance and risk assessment behavior in the rat. Cerebral infarcts were produced in rats by injecting small plastic beads into the left heart ventricle under short-acting anesthesia. The functional outcome was tested 24 h later by subjecting the animals to a series of consecutive behavioral tests. Thereafter, the rats were anesthetized and underwent magnetic resonance imaging. On average about seven infarcts per brain were found. The volume of the individual infarcts was largest in the hippocampus (mean=4.26 mm(3)) and smallest in the white matter (mean=0.83 mm(3)). Embolized animals performed spontaneous and evident locomotion. The activity was, however, significantly decreased compared to rats treated with vehicle. More specific tests for motor ability revealed reduced gait capacity and muscular strength. A significant relationship was found between behaviors reflecting motor ability and the total volume of infarcted tissue in the brain stem, cortex and cerebellum. Also the behavioral profile of risk and benefit assessment was found to be altered by the microembolization. It is concluded that the combination of the microembolization method and behavioral tests provides a valuable tool for further studies of the pathophysiology of, and potential treatment for, cerebral infarction.

Sodium excretion and renin secretion after continuous versus pulsatile infusion of oxytocin in rats.

Neurohypophyseal oxytocin (OT), secreted continuously under conditions of hyperosmolality, is a potent natriuretic hormone in rats. In contrast, OT secretion during lactation is pulsatile and is not accompanied by increased urinary Na+ excretion. The present experiments compared the effects of continuous and pulsatile infusion of OT on natriuresis in rats. In male rats anesthetized with Inactin, continuous infusion of OT (125 ng/kg·h) increased plasma OT to about 70 pg/ml; renal Na+ excretion increased 10-fold, and urine volume and K+ excretion also were elevated. However, when OT was administered iv in the same amount but in pulses given once every 5 or 10 min, to simulate the pattern of OT secretion during lactation, rats did not excrete significantly more urine, Na+, or K+ than did vehicle-treated animals. The plasma renin concentration, measured in these experiments because OT receptors are present in the macula densa, increased 2-fold when OT was infused either continuously or in pulses. These result...

Plasma vasopressin, oxytocin, estradiol, and progesterone related to water and sodium excretion in normal pregnancy and gestational hypertension

Objective. To investigate associations between plasma oxytocin and vasopressin concentrations and renal water and sodium excretion during normal pregnancy in comparison with gestational hypertension. Design. A prospective open trial conducted in the 12th, 24th, and 36th weeks of gestation. Settings. Seven antenatal clinics in Sweden. Participants. Thirty‐seven normotensive women, 15 women with gestational hypertension, and five women with mild preeclampsia. Main outcome measures. Hormones were analyzed with radioimmunoassay. Albumin, osmolality, sodium, and urea were analyzed by routine methods. Results. Blood pressure was elevated in the hypertensive women and body mass index in mild preeclampsia from week 12. Renal sodium excretion did not differ between groups or weeks and mean renal free water clearance was negative. In normotensive women, the vasopressin concentration was 1.1±0.2 (week 12) and 0.7±0.1 pmol/L (week 36: p = 0.053). In hypertensive women, vasopressin concentration was 1.7±1.0 pmol/L, week 12, and 0.7±0.1 pmol/L in week 36 (ns). In normotensive women, oxytocin concentration increased from 23±1 pmol/L in week 12 to 48±3 pmol/L in week 36 (p<0.001). Corresponding values in hypertensive women were 36±11 (week 12) and 55±5 pmol/L (week 36: ns). In all groups, plasma estradiol concentration increased. Plasma progesterone increased until week 24 in normotensive and hypertensive women with further increase in normotensive women. Conclusions. The low plasma vasopressin and increasing plasma oxytocin concentrations with unchanged water and sodium excretion indicate that oxytocin assists vasopressin in concentrating urine during pregnancy.

The C-peptide fragment EVARQ reduces glomerular hyperfiltration in streptozotocin-induced diabetic rats

Initially, diabetes is commonly associated with an increased glomerular filtration rate (GFR), a potential mechanism involved in the progression of diabetic nephropathy. Several studies have reported reno‐protective effects of C‐peptide. C‐peptide reduces diabetes‐induced hyperfiltration, as well as renal hypertrophy and albuminuria. In order to gain further understanding of these effects, it is very important to localize the active sites within the C‐peptide molecule. This study was designed to elucidate the effects of the C‐peptide fragment EVARQ on kidney function, blood pressure and blood glucose levels in diabetic rats in vivo.

Relationship between urinary albumin and albumin/creatinine ratio during normal pregnancy and pre-eclampsia.

Risberg A, Larsson A, Olsson K, Lyrenäs S, Sjöquist M. Relationship between urinary albumin and albumin/creatinine ratio during normal pregnancy and preeclampsia. 2004; 64: 17-24. Pre-eclampsia is a serious complication of pregnancy and it is important to detect the condition as early as possible. Albuminuria is an important symptom of pre-eclampsia and repeated urine analyses to screen for the condition are part of the standard antenatal care. The purpose of this study was to investigate whether measurement of the urine albumin/creatinine ratio in spot samples could be a complement to the dipstick method and could reduce the need for 24-h urine collections. Urine samples were collected for 24 h in weeks 12, 24 and 36 of pregnancy from both normotensive women and women who developed hypertension or who had pregnancy-induced hypertension (PIH) when they entered the study. The 24-h albumin excretion was significantly correlated to the albumin/creatinine ratio in all measurements (Pearson correlation coefficient). In week 12, the values were: n = 44, r = 0.964, p<0.001 (normotensive group) and in the PIH group: n = 8, r = 0.789, p<0.05. In week 24, the correlation values were r = 1.0 and p<0.001 in both the normotensive group (n = 41) and in the PiH group (n= 11). In week 36 the correlation values were r = 0.791 and p<0.00l in the normotensive group (n = 39) and r= 1.0 and p<0.001 in the PIH group (n= 16). Microalbuminuria was denned as urine albumin excretion higher than 30 mg/24 h and this corresponded to an albumin/creatinine ratio of 2.9. Microalbuminuria was found in three persons in the PIH group and in two persons in the normotensive group. Overt albuminuria (> 300 mg/24 h) was found in one of the 46 normotensive women (2%) and in 3 of the 19 PIH women (16%). In all these women the high albumin values had been detected by using the albumin/creatinine ratio method. In conclusion, it has been found that the albumin excretion in urine correlates significantly to the albumin/creatinine ratio during pregnancy. The urinary albumin/creatinine ratio appears to be a good alternative to the dipstick method and to 24-h urine collections.

The tubulo-glomerular feedback mechanism — a determinant for the autoregulation of the glomerular filtration rate in superficial and juxtamedullary nephrons

SummaryThe intrinsic myogenic hypothesis and the tubuloglomerular feedback mechanism (TGF) give the presently most cherished explanation to the autoregulation of renal blood flow and glomerular filtration rate. A series of experiments was performed on young, normohydrated rats in order to evaluate the importance of TGF as an autoregulatory factor of the single nephron glomerular filtration rate (SNGFR) in superficial and juxtamedullary nephron populations. Micropuncture techniques were applied to tubular structures of the renal surface and on the papilla for the measurement of hydrostatic pressures and SNGFR. The SNGFR was also measured with a modified Hanssen technique. A TV-technique was used to record the urine free flow rate in the loop of Henle.The net driving forces for glomerular filtration at the afferent end of the glomerular capillaries were estimated to be 19 and 47 mm Hg for superficial and juxtamedullary nephrons respectively, when the urine flow at the macula densa was zero. The SNGFR of the two nephron populations amounted to 29.6 and 84.1 nl·min−1·g−1 K.W., as measured with the micropuncture technique. With a modified Hanssen technique the corresponding values were 25.8 and 27.7 nl·min−1. g−1 K.W. (kidney weight).The SNGFR was found to be well autoregulated when the urine flow at the macula densa was intact, but not when the urine flow was interrupted.The flow rate in the loop of Henle was in free flow conditions 7.3 nl·min−1·g−1 K.W. which shall be compared with 19.2 nl·min−1·g−1 K.W. when the urine flow to the macula densa was zero.We conclude that SNGFR is mainly autoregulated by the TGF-mechanism in young, normohydrated rats at lower arterial pressures. In normal conditions TGF is highly activated for juxtamedullary nephrons, but not for the superficial ones. The high urine flow rate in the loop of Henle at reduced flow rates at the macula densa may invalidate the use of loop blockade in studies of water and solute transfer across the loop walls.ZusammenfassungDas Phänomen der Autoregulation der Nierendurchblutung und des Glomerulumfiltrats lassen sich zur Zeit am besten mit myogenen Mechanismen und mit Hilfe des tubuloglomerulären Feedbackmechanismus erklären. Es wurden Untersuchungen an jungen Ratten durchgeführt, um die Bedeutung des tubuloglomerulären Feedbacks bei der Autoregulation in Nephronen der Nierenrinde und des Nierenmarkes weiter aufzuklären. Hierzu wurde die Mikropunktionstechnik am Einzelnephron an der Oberfläche der Niere und an der Nierenpapille verwendet, um sowohl den Druck im Glomerulum als auch die Einzelnephronfiltrationsrate (SN-GFR) zu messen. Außerdem verwendeten wir zur Bestimmung der SN-GFR in einer anderen Versuchsserie die modifizierte Hanssen-Technik, d.h. Bestimmung der SN-GFR nach Bolusinjektion eines Farbindikators und Dissektion des Einzelnephrons. Weiterhin entwickelten wir eine Fernseh-Videotechnik zur Bestimmung der spontanen Harnflußrate an intakten Henleschen Schleifen in vivo.SN-GFR Messungen der beiden Nephronpopulationen ergaben bei Blockade des Harnflusses an der Macula densa 29.6 nl·min−1·g−1 Nierengewicht für die oberflächlichen Nephrone und 84.1 für die tiefen Nephrone, wenn man diese mit der Mikropunktionstechnik bestimmt. Der Nettofiltrationsdruck an oberflächlichen Nephronen wurde mit 19 und an tiefen mit 47 mm Hg bestimmt, ebenfalls bei blockiertem Harnfluß zur Macula densa. Die modifizierte Hanssentechnik dagegen ergab für die SN-GFR der oberflächlichen Nephrone 25,8 nl·min−1·g−1 Nierengewicht und für die tiefen 27,7. Diese Werte entsprechen dem Zustand des intakten, physiologischen Harnflusses an der Macula densa. Die SN-GFR war bei intaktem Harnstrom an der Macula densa (Hanssentechnik) gut autoreguliert, während sie das nicht war bei blockiertem Harnstrom an der Macula densa (Mikropunktionstechnik). Die Videotechnik ergab in der Henleschen Schleife einen spontanen Volumenfluß von 7,3 nl·min−1·g−1 und dieser stieg bei Blockierung des Flusses zur Macula densa auf 19,2 nl·min−1·g−1 an.Unsere Versuche zeigen, daß hauptsächlich der tubuloglomeruläre Feedback zur Autoregulation der Einzelnephronfiltrationsrate bei jungen, normal hydrierten Ratten beiträgt. Der tubuloglomeruläre Feedback ist vor allem in den tiefen Nephronen von Bedeutung und muß bei Untersuchungen an Henleschen Schleifen von tiefen Nephronen berücksichtigt werden.

Plasma bikunin: half-life and tissue uptake.

Bikunin is a chondroitin sulfate-containing plasma protein synthesized in the liver. In vitro, it has been shown to inhibit proteases and to have additional activities, but its biological function is still unclear. Here we have studied the dynamics of plasma bikunin in rats and mice. A half-life of 7 ± 2 min was obtained from the time course of the decrease of the plasma level of bikunin following hepatectomy. Clearance experiments with intravenously injected radiolabeled bikunin with or without the chondroitin sulfate chain showed that the polysaccharide had little influence on the elimination rate of the protein. The uptake of bikunin by different tissues was studied using bikunin labeled with the residualizing agent 125I-tyramine cellobiose; 60 min after intravenous injection, 49% of the radioactivity was recovered in the kidneys and 6–11% in the liver, bones, skin, intestine and skeletal muscle. The uptake in the liver was analyzed by intravenous injection of radiolabeled bikunin followed by collagenase perfusion and dispersion of the liver cells. These experiments indicated that bikunin is first trapped extracellularly within the liver before being internalized by the cells. (Mol Cell Biochem 271: 61–67, 2005)