Biomedical subjects

P D Walker

Publications and source records attributed to P D Walker.

At least 19 recordsLinked to original sources

PubMed2000

Stimulated serotonin release from hyperinnervated terminals subsequent to neonatal dopamine depletion regulates striatal tachykinin, but not enkephalin gene expression.

Dopamine (DA) depletion in neonatal rodents results in depressed tachykinin and elevated enkephalin gene expression in the adult striatum (STR). Concurrently, serotonin (5-HT) fibers sprout to hyperinnervate the DA-depleted anterior striatum (A-STR). The present study was designed to determine if increased 5-HT release from sprouted terminals influences dysregulated preprotachykinin (PPT) and preproenkephalin (PPE) mRNA expression in the DA-depleted STR. Three-day-old Sprague-Dawley rat pups received bilateral intracerebroventricular injections of vehicle or the DA neurotoxin 6-hydroxydopamine (6-OHDA, 100 microg). Two months later, rats received a single intraperitoneal injection of vehicle or the acute 5-HT releasing agent p-chloroamphetamine (PCA; 10 mg/kg). Rats were killed 4 h later and striata processed for monoamine content by HPLC-ED and mRNA expression by in situ hybridization within specific subregions of the A-STR and posterior striatum (P-STR). 6-OHDA treatment severely (>98%) reduced striatal DA levels, while 5-HT content in the A-STR was significantly elevated (doubled), indicative of 5-HT hyperinnervation. Following 6-OHDA, PPT mRNA levels were depressed 60-66% across three subregions of the A-STR and 52-59% across two subregions of the P-STR, while PPE mRNA expression was elevated in both the A-STR (50-62%) and P-STR (55-82%). PCA normalized PPT mRNA levels in all regions of the DA-depleted A-STR and P-STR, yet did not alter PPE levels in either dorsal central or medial regions from 6-OHDA alone, but reduced PPE to control levels in the dorsal lateral A-STR. These data indicate that increased 5-HT neurotransmission, following neonatal 6-OHDA treatment, primarily influences PPT-containing neurons of the direct striatal output pathway.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2000

Acute rejection presenting as nephrotic syndrome.

BACKGROUND: Early diagnosis and treatment of acute rejection is important to prevent continued renal injury. Acute rejection most commonly presents with asymptomatic rise in serum creatinine. Proteinuria associated with acute rejection is well established; however, there is limited documentation of the presentation of acute rejection as nephrotic syndrome in the literature. METHODS AND RESULTS: We report a renal transplant patient who presented with early onset nephrotic syndrome without change in serum creatinine, whose allograft biopsy confirmed acute glomerulitis and vascular rejection. Treatment of the acute rejection was accompanied by resolution of the nephrotic syndrome. A second episode of acute rejection was also manifested as nephrotic range proteinuria. CONCLUSION: The nephrotic syndrome in early post-transplantation period should prompt a work-up for acute rejection even in the absence of the common findings of this complication.

Acute Disease↗

PubMed2000

Cyclic AMP regulates substance P expression in developing and mature spinal sensory neurons.

The tachykinin, substance P, has long been associated with transmission of noxious stimuli. However, relatively little is known about signal transduction pathways subserving peptidergic regulation in sensory neurons. To investigate whether cyclic AMP (cAMP) could be a potential second messenger subserving substance P expression, dorsal root ganglion neurons were grown in culture in the presence of agents that increase content of cAMP. In developing neurons, forskolin increased substance P content and survival almost threefold. Anti-nerve growth factor (NGF) blocked the effect of NGF but not forskolin, suggesting that increased cAMP acts directly and not via increased secretion of NGF from Schwann cells and fibroblasts. In adult neurons, which do not require supplemental trophic factors for survival, NGF and forskolin had similar effects on substance P levels. Neither agent had any effect on somatostatin content of either developing or mature sensory neurons. 8-bromo cAMP and isobutyl methylxanthine duplicated the action of forskolin. Further, all three agents increased expression of preprotachykinin mRNA. Forskolin appeared to increase both total and neuron-specific expression of message as well as the number of neurons expressing mRNA. Our results suggest that cAMP directly regulates substance P content in sensory neurons from adult and neonatal rats.

1-Methyl-3-isobutylxanthine↗

PubMed2000

Serotonin 2A and 2C receptor biosynthesis in the rodent striatum during postnatal development: mRNA expression and functional linkage to neuropeptide gene regulation.

The present study was designed to determine if there are region-specific differences in serotonin (5-HT) neurotransmission and 5-HT receptor expression that may limit the stimulatory effects of the 5-HT releaser p-chloroamphetamine (pCA) on striatal neuropeptide gene expression to the posterior striatum (P-STR) during postnatal maturation. Sprague-Dawley rat brains from postnatal days (PND) 1-35 were processed for 5-HT(2A) and 5-HT(2C) receptor mRNA expression by in situ hybridization and monoamine analysis by HPLC. Within the P-STR, 5-HT(2A) receptor mRNA expression reached young adult (PND 35) levels by PND 3, while levels in the A-STR were significantly less (range: 1.43 +/- 0.219-6. 36 +/- 0.478) than P-STR (5.36 +/- 0.854-12.11 +/- 1.08) at each respective age throughout the time course. 5-HT(2C) receptor mRNA expression reached young adult levels at PND 7 in the A-STR and by PND 3 in the P-STR. At each PND age 5-HT(2C) receptor mRNA levels within the P-STR were significantly less (6.23 +/- 1.02-12.32 +/- 0.427) than the A-STR (7.31 +/- 1.65-26.84 +/- 2.24). 5-HT content increased across the developmental time course within the P-STR (5.01 +/- 0.327-15.7 +/- 1.03 ng/mg protein) and A-STR (2.97 +/- 0. 223-11.2 +/- 0.701 ng/mg protein). Four hours following injection (i. p.) of pCA (10 mg/kg), preprotachykinin (PPT) mRNA levels increased 89% in the P-STR but not the anterior (A-STR) striatum of the 3-week-old rat, which were prevented by preinjection (30 min, i.p.) of the 5-HT(2) receptor antagonist ritanserin (1 mg/kg). Together, these data suggest that faster maturity of 5-HT(2A) receptor expression in the P-STR may be sufficient to convey the region-specific acute stimulatory effects of pCA on PPT mRNA transcription in the developing rodent striatum. These results provide further evidence that the influence of 5-HT on neuropeptide gene expression is far stronger in caudal vs. rostral striatal regions during postnatal development.

Animals↗

PubMed2000

Feasibility study of multicentre comparison of NHS hospital pharmacy computer data.

AIMS: This study aims to determine the feasibility of collecting, collating and analysing drug expenditure data from a sample of acute hospitals in England. METHODS: The hospital pharmacy computer system was used to report on drug expenditure from 16 hospitals throughout England for a 2 year period. These data were analysed as a whole and hospital episode statistics were correlated to hospital drug costs. RESULTS: Hospital outpatient costs were found to be approximately one third of hospital inpatient costs. Cardiovascular drugs accounted for the greatest increase in expenditure for both inpatients and outpatients (25%). The most expensive therapeutic area of drug use across all sites was anti-infectives. The average daily number of occupied beds explained 55% of the variation in inpatient expenditure and the number of outpatient (including Accident and Emergency) attendances explained 60% of the outpatient drug expenditure. CONCLUSIONS: This project has confirmed the feasibility of collecting, collating and analysing hospital drug expenditure and identified some interesting patterns and trends in hospital drug use. Hospital activity is reflected in hospital drug costs.

Clinical Pharmacy Information Systems↗

PubMed2000

Real-time analysis of preprotachykinin promoter activity in single cortical neurons.

Technological limitations have hindered the study of gene elements regulating transcription within CNS neurons. In the present stuides, rat cortical brain slices endogenously expressing the preprotachykinin (PPT) gene were transfected with gene constructs encompassing green fluorescent protein (GFP) under the control of the PPT promoter. These slices were maintained in organotypic culture so that the fluorescence intensity within individual living cells could be quantified using laser scanning confocal microscopy before and after application of stimulatory agents. Combined treatment with forskolin and elevated potassium significantly increased expression of both endogenous PPT mRNA and the PPT promoter-GFP construct. The ability to follow fluorescence changes within single neurons in real time offers a powerful "within-subject" experimental approach for analysis of neural gene promoters.

Animals↗

PubMed2000

Evidence for peroxynitrite formation in renal ischemia-reperfusion injury: studies with the inducible nitric oxide synthase inhibitor L-N(6)-(1-Iminoethyl)lysine.

Reactive oxygen species are suggested to participate in ischemia-reperfusion (I-R) injury. However, induction of inducible nitric oxide synthase (iNOS) and production of high levels of nitric oxide (NO) also contribute to this injury. NO can combine with superoxide to form the potent oxidant peroxynitrite (ONOO(-)). NO and ONOO(-) were investigated in a rat model of renal I-R injury using the selective iNOS inhibitor L-N(6)-(1-iminoethyl)lysine (L-NIL). Sprague-Dawley rats were subjected to 40 min of bilateral renal ischemia followed by 6 h of reperfusion with or without L-NIL administration. Control animals received a sham surgery and had plasma creatinine values of 0.4 +/- 0.1 mg/dl. I-R surgery significantly increased plasma creatinine levels to 1.9 +/- 0.3 mg/dl (P <.05) and caused renal cortical necrosis. L-NIL administration (3 mg/kg) in animals subjected to I-R significantly decreased plasma creatinine levels to 1.2 +/- 0.10 mg/dl (P <.05 compared with I-R) and reduced tubular damage. ONOO(-) formation was evaluated by detecting 3-nitrotyrosine-protein adducts, a stable biomarker of ONOO(-) formation. Immunohistochemistry and HPLC revealed that the kidneys from I-R animals had increased levels of 3-nitrotyrosine-protein adducts compared with control animals. L-NIL-treated rats (3 mg/kg) subjected to I-R showed decreased levels of 3-nitrotyrosine-protein adducts. These results support the hypothesis that iNOS-generated NO mediates damage in I-R injury possibly through ONOO(-) formation.

Animals↗

PubMed1999

Suppression of serotonin hyperinnervation does not alter the dysregulatory influences of dopamine depletion on striatal neuropeptide gene expression in rodent neonates.

Sixty days following neonatal dopamine depletion (>98%) with 6-hydroxydopamine, preprotachykinin and preprodynorphin mRNA levels were significantly reduced (67 and 78% of vehicle controls, respectively) in the anterior striatum as determined by in situ hybridization while preproenkephalin mRNA expression was elevated (133% of vehicle controls). Suppression of the serotonin hyperinnervation phenomenon in the dopamine-depleted rat with 5,7-dihydroxytryptamine yielded no significant alterations in reduced striatal preprotachykinin (66%) or preprodynorphin (64%) mRNA levels, while preproenkephalin mRNA expression remained significantly elevated (140%). These data suggest that striatal serotonin hyperinnervation does not contribute to the development of dysregulated striatal neuropeptide transmission in either direct or indirect striatal output pathways following neonatal dopamine depletion.

5,7-Dihydroxytryptamine↗

PubMed1999

Serotonin 2A receptor mRNA levels in the neonatal dopamine-depleted rat striatum remain upregulated following suppression of serotonin hyperinnervation.

Sixty days after bilateral dopamine (DA) depletion (>98%) with 6-hydroxydopamine (6-OHDA) in neonatal rats, serotonin (5-HT) content doubled and 5-HT(2A) receptor mRNA expression rose 54% within the rostral striatum. To determine if striatal 5-HT(2A) receptor mRNA upregulation is dependent on increased 5-HT levels following DA depletion, neonatal rats received dual injections of 6-OHDA and 5,7-dihydroxytryptamine (5,7-DHT) which suppressed 5-HT content by approximately 90%. In these 6-OHDA/5,7-DHT-treated rats, striatal 5-HT(2A) receptor mRNA expression was still elevated (87% above vehicle controls). Comparative analysis of 5-HT(2C) receptor mRNA expression yielded no significant changes in any experimental group. These results demonstrate that upregulated 5-HT(2A) receptor biosynthesis in the DA-depleted rat is not dependent on subsequent 5-HT hyperinnervation.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1999

Synergistic interaction between serotonin-2 receptor and dopamine D1 receptor stimulation on striatal preprotachykinin mRNA expression in the 6-hydroxydopamine lesioned rat.

The regulation of striatal preprotachykinin (PPT) mRNA expression can be mediated through both dopamine (DA) D1 and serotonin (5-HT) 5-HT2A/2C receptors. In the present study, we used in situ hybridization to examine possible synergistic interactions between 5-HT2A/2C and D1 receptor-mediated regulation of striatal PPT mRNA levels in the rat depleted of DA with 6-hydroxydopamine. Acute administration of the 5-HT2A/2C receptor agonist DOI (2 mg/kg) significantly increased (+75%) PPT mRNA levels in the dorsal striatum. Acute administration of the D1 receptor agonist SKF-38393 (2 mg/kg) did not significantly alter PPT mRNA levels in the dorsal striatum. However, the co-administration of SKF-38393 and DOI produced a significant increase (+300%) in striatal PPT mRNA expression restricted to the periventricular region of the dorsal-medial striatum. This synergistic interaction was not observed in the remaining aspect of the dorsal striatum where DOI alone increased PPT mRNA expression. These data show that 5-HT2A/2C and D1 receptors can act in a synergistic manner to regulate striatal PPT mRNA in a subregion of the DA-depleted striatum.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed1999

Acute p-chloroamphetamine increases striatal preprotachykinin mRNA: role of the serotonin 2A/2C receptor.

Acute administration of p-chloroamphetamine (pCA) significantly increased (+90%) preprotachykinin (PPT) mRNA levels in the rat striatum. Administration of the serotonin2A/2C receptor antagonist, ritanserin, blocked the pCA-induced increase in PPT mRNA levels. alpha-Methyl-p-tyrosine pretreatment (alpha-MT, to reduce dopamine transmission) inhibited the pCA-induced increase in PPT mRNA levels. These results indicate that the pCA-induced increase in striatal PPT mRNA expression is mediated by serotonin2A/2C receptors but also requires dopamine tone.

Animals↗

PubMed1999

Differential sensitivity of tachykinin vs. enkephalin gene expression in the posterior striatum in response to acute p-chloroamphetamine treatment during postnatal development.

The acute effects of the monoamine releaser p-chloroamphetamine (pCA, 10 mg/kg, i.p.) on preprotachykinin (PPT) and preproenkephalin (PPE) mRNA expression in the anterior (A-STR) vs. posterior (P-STR) striatum were studied in rodents at postnatal days (PND) 10, 21 and 35. Northern analysis 4 h post-injection yielded no significant mRNA changes within the A-STR of any pCA group. However, significant increases (80-200% of saline control) in PPT mRNA levels occurred within the P-STR at all three postnatal ages. Interestingly, pCA did not increase PPE mRNA levels within the P-STR until PND 35 (150% of saline control). Such observation suggests that tachykinin neurons of the P-STR achieve an earlier monoamine-responsive signal transduction linkage to gene regulation as compared to enkephalin neurons. Given its predominance in the caudal regions of the striatum, 5-HT neurotransmission at the 5-HT2 receptor is suggested to play a central role in this mechanism.

Aging↗

PubMed1999

Effects of serotonin inhibition on neuronal and astrocyte plasticity in the phrenic nucleus 4 h following C2 spinal cord hemisection.

C2 spinal cord hemisection results in synaptic and astroglial changes in the phrenic nucleus which have been associated with the recovery of the ipsilateral hemidiaphragm during expression of the crossed phrenic phenomenon. As part of our ongoing analysis of the neurotransmitters involved, the present study investigated the effects of systemic administration of para-chlorophenylalanine (p-CPA), a serotonin (5-HT) synthesis inhibitor, on plasticity in the rat phrenic nucleus 4 h following C2 hemisection. Hemisected control rats demonstrated typical morphological changes in the ipsilateral phrenic nucleus including: (1) an increased number and length of synaptic active zones and (2) an increased number and length of dendrodendritic membrane appositions. p-CPA treatment 3 days prior to hemisection reduced 5-HT levels and resulted in an attenuation of these changes in the ipsilateral phrenic nucleus 4 h following hemisection compared to hemisected controls. In addition, p-CPA treatment attenuated injury-induced alterations in immunohistochemical staining of glial fibrillary acidic protein (GFAP), although Western blot analysis demonstrated that overall levels of GFAP did not differ significantly between groups. The results suggest that inhibition of 5-HT synthesis by p-CPA attenuates hemisection-induced plasticity in the phrenic nucleus 4 h following an ipsilateral C2 hemisection.

Animals↗

PubMed1999

Effects of the serotonin synthesis inhibitor p-CPA on the expression of the crossed phrenic phenomenon 4 h following C2 spinal cord hemisection.

The present study assesses the effects of para-chlorophenylalanine (p-CPA), a serotonin-depleting drug, on the recovery of respiratory-related activity in the phrenic nerve induced by asphyxia 4 h following ipsilateral C2 hemisection in young adult rats. HPLC analysis was used to quantify levels of serotonin (5-HT), dopamine (DA), norepinephrine, and the 5-HT metabolite, 5-hydroxyindoleacetic acid, in the C4 segment of the spinal cord, all of which were significantly lower in p-CPA-treated hemisected rats compared to hemisected controls receiving saline. Hemisection alone was found to significantly increase 5-HT levels and significantly decrease DA levels compared to normal controls. Eight of eight saline-injected rats expressed recovery of respiratory-related activity in the ipsilateral phrenic nerve during asphyxia 4 h following hemisection, while only 4/8 rats in the p-CPA-treated group expressed recovery in the ipsilateral nerve. Quantification of integrated phrenic nerve wave-forms indicated that the mean amplitude of respiratory-related activity in the ipsilateral phrenic nerve was significantly lower in p-CPA-treated rats than in saline controls. In addition, saline controls demonstrated significant increases in mean respiratory frequency and mean amplitude of contralateral phrenic nerve activity during asphyxia, compared to normocapnia. However, p-CPA-treated rats did not express significant differences in either mean respiratory frequency or mean amplitude of integrated respiratory wave-forms during asphyxia, compared to normocapnia. The results suggest that p-CPA treatment attenuates the recovery of respiratory-related activity in the phrenic nerve 4 h following ipsilateral C2 hemisection and attenuates asphyxia-induced increases in respiratory frequency and respiratory burst amplitude recorded from the contralateral phrenic nerve.

Animals↗

PubMed1999

Serotonin-2 receptor stimulation normalizes striatal preprotachykinin messenger RNA in an animal model of Parkinson's disease.

Dopamine and serotonin neurotransmission regulate striatal preprotachykinin messenger RNA levels. In the present study, we investigated serotonin 2A/2C receptor-mediated regulation of preprotachykinin messenger RNA expression in the rat striatum after adult dopamine depletion produced with 6-hydroxydopamine. Significant reductions (46-61% of control values) in preprotachykinin messenger RNA levels were detected by in situ hybridization in rostral, central and caudal regions of the striatum after >85% dopamine depletion. Repeated administration of the specific serotonin2A/2C receptor agonist, (+/-)-2,5-dimethoxy-4-iodoamphetamine hydrobromide, to dopamine-depleted rats completely reversed the reduction in preprotachykinin messenger RNA levels in rostral, central and dorsal-caudal striatal regions. In unlesioned (vehicle-injected) control animals, repeated administration of (+/-)-2,5-dimethoxy-4-iodoamphetamine hydrobromide did not affect preprotachykinin messenger RNA expression in rostral, central and ventral-caudal striatal regions, but decreased preprotachykinin messenger RNA levels in the dorsal-caudal striatal subregion. In addition, serotonin turnover in the dopamine-depleted rostral striatum was significantly increased by 35-45% which is consistent with serotonin hyperinnervation after 6-hydroxydopamine lesions. These data show that the decrease in striatal preprotachykinin messenger RNA after dopamine depletion can be normalized with repeated serotonin2A/2C receptor stimulation. We hypothesize that this serotonin2A/2C receptor regulation of preprotachykinin messenger RNA expression after 6-hydroxydopamine is a consequence of serotonin hyperinnervation, which may include increased striatal serotonin2A/2C receptors, induced by dopamine depletion. We also propose that the serotonin system could be pharmacologically targeted to restore the direct striatal tachykinin pathway in Parkinson's disease.

Amphetamines↗

PubMed1999

Patterns of immediate early gene mRNA expression following rodent and human traumatic brain injury.

Cell stimulation which leads to degeneration triggers a prolonged wave of immediate early gene (IEG) transcription that correlates with neuronal demise. In order to determine the relevance of the prolonged IEG response to human traumatic brain injury, we analyzed IEG mRNA levels in brain tissue isolated following a controlled penetrating injury and an injection of the excitotoxin Quinolinic acid (QA), as well as from tissue recovered during routine neurosurgery for trauma. Total RNA was extracted from tissue and subjected to Northern analysis of IEG mRNAs (c-fos and zif/268). Both models produced rapid and prolonged waves of IEG transcription that appeared to correlate with the severity of injury. Increases in zif/268 mRNA were observed within 1 h with levels reaching their peak at 6 h following excitotoxic injury and 3 h following a controlled penetration. In general, human traumatic brain injury resulted in variable increases in IEG mRNA levels following traumatic injury with the largest IEG mRNA increases observed in tissue collected 0-10 h after injury. This post-injury time corresponds to the peak of the prolonged IEG response observed in rodents following excitotoxic injury. Comparisons were made in IEG response between rodent frontal cortex and human cortex, because the majority of the human tissue originated from the cerebral cortex. These results further support the hypothesis that prolonged IEG transcription serves as a marker of traumatic brain injury and may play a role in neurodegeneration and/or glial activation. Moreover, observations of similar IEG patterns of expression reinforces the importance of rodent models of brain injury providing useful information directly applicable to human brain injury.

Animals↗

PubMed1999

Oxidant mechanisms in toxic acute renal failure.

Over the last decade, there is accumulating evidence for a role of reactive oxygen metabolites in the pathogenesis of a variety of renal diseases, including gentamicin, glycerol, cisplatin, and cyclosporine A models of toxic acute renal failure. Gentamicin has been shown both in in vitro and in vivo studies to enhance the generation of reactive oxygen metabolites. Iron is important in models of tissue injury, presumably because it is capable of catalyzing free-radical formation. Gentamicin has been shown to cause release of iron from renal cortical mitochondria. Scavengers of reactive oxygen metabolites as well as iron chelators provide protection in gentamicin-induced nephrotoxicity. In glycerol-induced acute renal failure, an animal model of rhabdomyolysis, there is enhanced generation of hydrogen peroxide, and scavengers of reactive oxygen metabolites and iron chelators provide protection. Although the dogma is that the myoglobin is the source of iron, recent studies suggest that cytochrome P450 may be an important source of iron in this model. In addition, there are marked alterations in antioxidant defenses, such as glutathione, as well as changes in heme oxygenase. Several recent in vitro and in vivo studies indicate an important role of reactive oxygen metabolites in cisplatin-induced nephrotoxicity. Thus, catalytic iron is increased both in vitro and in vivo by cisplatin, and iron chelators as well as hydroxyl radical scavengers have been shown to be protective. Recent studies indicate that cytochrome P450 may also be an important source of the catalytic iron in cisplatin nephrotoxicity. Cyclosporine A has been shown to enhance generation of hydrogen peroxide in vitro and enhance lipid peroxidation in vitro and in vivo. Antioxidants have been shown to be protective in cyclosporine A nephrotoxicity. This collective body of evidence suggests an important role for reactive oxygen metabolites in toxic acute renal failure and may provide therapeutic opportunities of preventing or treating acute renal failure in humans.

Acute Kidney Injury↗

PubMed1998

Meprin A, the major matrix degrading enzyme in renal tubules, produces a novel nidogen fragment in vitro and in vivo.

We examined the effect of meprin A, the major matrix degrading metalloproteinase in rat kidney, on the laminin-nidogen complex. N-terminal sequence information from the most abundant 55 kDa fragment revealed that it was a breakdown product of nidogen rather than laminin. In comparison with over 50 nidogen cleavage sites produced by other proteases, the meprin A-induced nidogen cleavage site at amino acid position 899-900, a glutamine-glycine site in the G3 domain, is unique. In addition, these data demonstrate that meprin A degrades the G3 domain of nidogen even in the presence of laminin binding, which usually accords protection from proteolytic degradation. Meprin A also degraded purified nidogen into similar breakdown products. Given that the tubular basement membrane is located on the basilar side of the cell, the location of meprin A on the apical brush border makes it difficult to envision a role for meprin A in injury-induced basement membrane component breakdown. Thus, we examined the possibility that following renal tubular epithelial cell injury, meprin A undergoes a translocation to reach the underlying basement membrane. After renal ischemia-reperfusion there was a marked alteration in meprin A staining with meprin A now distributed throughout the renal tubular cell cytoplasm and directly adherent to the tubular basement membrane. This was in contrast to the usual linear staining of the brush border of tubules in the corticomedullary junction. These data provide unequivocal evidence that following injury, meprin A undergoes redistribution and/or adherence to the tubular basement membrane. Since in our in vitro studies, we identified a distinct meprin-induced 55 kDa nidogen breakdown product, the urine was also examined for the presence of nidogen degradation products after rat renal ischemia-reperfusion injury. Western blots showed a marked increase in the urinary 55 kDa nidogen fragment as early as the first day following ischemia-reperfusion injury and continuing for six days. Taken together, these in vivo data strongly support the notion that the nidogen breakdown products are the result of partial degradation of tubular basement membrane by meprin A following renal tubular ischemia-reperfusion injury.

Amino Acid Sequence↗