Mitogenic effects of certain cathepsins and calciferin on the intact liver in vivo

Calciferin, a new parathyroid hormone stimulating the release of cathepsins D and L (but not B) from isolated lysosomes, or the release of cathepsin D from erythrocytes or ghosts in vitro, elevated free cathepsin D in the blood, and at the same time stimulated DNA synthesis in the intact liver when it was injected into mice. Both calciferin and free cathepsin D in the blood (rats) were elevated concomitantly soon after 70% hepatectomy, reaching a peak around 5 hr. The cathepsin D-elevation was almost proportional to fractional hepatectomies. Cathepsin L (but not B), when injected intraperitoneally into mice, stimulated DNA synthesis and mitosis in the intact liver much like cathepsin D, the effect of which was reported earlier. In contrast to the mitogenic effects of calciferin or cathepsins (D and L) in vivo, only cathepsin L (but not cathepsin D or calciferin) in low concentrations appeared to stimulate DNA synthesis in the cultured liver cells, and also stimulated adenylate cyclase of isolated liver plasma membranes in vitro. Dibutyryl-cyclic AMP in concentrations lower than 10(-5) M also stimulated DNA synthesis in cultured liver cells.     

Unique cathepsin D-type proteases in rat thoracic duct lymphocytes and in rat lymphoid tissues.

Two unique cathepsin D-type proteases apparently present only in rat thoracic duct lymphocytes and in rat lymphoid tissues are described. One, termed H enzyme, has an apparent molecular weight of similar to95,000; the other, termed L enzyme, has an apparent molecular weight of similar to45,000, in common with that of most cathepsins D from other tissues and species. Both enzymes differ from cathepsin D, however, by a considerably greater sensitivity to inhibition by pepstatin and by a smaller degree of inhibition by an antiserum which inhibits rat liver cathepsin D. H enzyme is converted to L enzyme by treatment with beta-mercaptoethanol; the relationship between the two enzymes remains unknown. H and L enzyme have been detected in rat lymphoid tissues and in mouse spleen, but they are not present in other rat tissues (liver, kidney, adrenals), rabbit tissues, calf thymus, bovine spleen, or human tonsils. As measured on acid-denatured bovine hemoglobin as substrate, both enzymes have pH activity curves identical with that of rat liver cathepsin D, with optimal activity at pH 3.6. Activity on human serum albumin is much less and also shows an optimum at pH 3.6; hence, neither enzyme has the properties of cathepsin E. Thiol-reactive inhibitiors have no effect on the activity of H and L enzyme; thus they do not belong to the B group of cathepsins. Additional information, discussed in this paper, leads us to conclude that partially purified H and L enzymes are cathepsin D-type proteases.     

Lysosomal cathepsins B, L, and D in the development of murine experimental leukemias

Lysosomal proteases are actively involved into pathogenesis of malignant tumors. Impairments in the interaction between proteases and their inhibitors are implicated in the processes of tumor invasion and metastasis. Among proteases associated with malignant growth, cysteine cathepsins B and L and aspartic cathepsin D are considered to play the major role in the tumor development. The present study was designed to investigate the activity of cathepsins B, L, and D during the development and treatment of murine experimental leukemias and to determine correlation between these proteases and course of pathological process as well as efficiency of the chemotherapeutic treatment. P-388 leukemia was characterized by a more aggressive development and unfavorable prognosis than L1210/1 leukemia. In mice with P-388 leukemia the activity of lysosomal cathepsins B, D, and L in the tumor tissue, liver and spleen, as well as the activity of cathepsins B and L in serum were lower than activities of these enzymes in mice with L1210/1 leukemia. Changes in the activity of cathepsins in liver and spleen of leukemic mice reflected a level of aggressiveness of the tumor development and invasion of these organs with tumor cells. Treatment of these experimental leukemias resulted in the increase of cathepsin B, L and D activity in the tumor tissue, liver, spleen and the increase in cathepsin B and L activity in serum. The highest protease activity was detected in the groups of mice characterized by the highest inhibition of the tumor growth. These data demonstrate that lysosomal proteases are involved in the progression of murine experimental leukemias and elimination of tumor cells in the result of treatment. Thus, determination of the activity of cysteine and aspartic proteases can be used for evaluation of cancer malignancy, tumor sensitivity for chemotherapy and efficiency of treatment.     

Activity of "nonspecific pancreatic carboxylesterase" in rat serum in experimentally induced acute pancreatitis (preliminary results)

The aim of this study was to obtain more information on the serum level of "nonspecific pancreatic carboxylesterase" (PCE) in experimentally induced acute pancreatitis in rats. The effects of caerulein stimulation, hepatic duct ligation, bile-pancreatic duct ligation or the effect of retrograde injection of saline, 5% taurocholate and sunflower oil were investigated. The activity of PCE and amylase was measured in the serum, pancreatic tissue, pancreatic juice and ascitic fluid. The changes in PCE activity were greater (both in directions to increase or decrease) than that of amylase, produced by different experimental procedures. The results confirm the thesis that the serum activity of PCE is a more sensitive diagnostic method than that of amylase to detect the inflammatory process in the pancreas or the effect of obstruction of the pancreatic duct.     

Toxic effects of different concentrations of dimethoate on lysosomal enzymes of female albino rats.

The effect of three different concentrations of dimethoate on the activity of certain lysosomal enzymes, viz. beta-glucuronidase, beta-N-acetylglucosaminidase, cathepsin B and cathepsin D in serum, skin, liver, kidney and spleen and the stability of liver and kidney lysosomes was studied in female albino rats. The activity of beta-glucuronidase, beta-N-acetylglucosaminidase, cathepsin D was found to increase in serum and tissues in higher concentration (2.25 mg/100 g body weight) of dimethoate treated rats. A significant increase in the rate of release of beta-glucuronidase was found in the liver and kidney of higher concentration of dimethoate treated rats compared to controls. The results demonstrate that the activity of lysosomal enzymes increased in higher concentration of dimethoate treated rats than the lower concentration (0.56 mg/100 g body weight) of dimethoate treated rats.     

Preventive role of gallic acid on alcohol dependent and cysteine protease-mediated pancreas injury

In order to investigate an association between alcohol consumption and lysosomal cysteine protease induced pancreatic injury and preventive effect of gallic acid as dose-dependent, we determined myeloperoxidase and malondialdehyde levels, serum amylase activities and cathepsin B and L activities in the cytosolic and lysosomal fractions of pancreatic tissue in the ethanol (8?g/kg) and ethanol plus gallic acid (at different doses 50, 100 and 200?mg/kg) given rats. Absolute ethanol (8?g/kg) was given by oral gavage. Gallic acid was dissolved in the saline (2?ml/kg) and administered before 30?min the oral administration of ethanol. Pancreatic myeloperoxidase and also malondialdehyde levels and serum amylase activities were measured. Besides, histological investigations were made. Cathepsin B activities in the cytosolic fraction were decreased by gallic acid (200?mg/kg) and increased in ethanol given rats. Cytosolic/lysosomal ratio of cathepsin B and L were found to be low in the all doses of gallic acid as compared to ethanol group. Serum amylase, pancreatic myeloperoxidase activities and malondialdehyde levels in the ethanol group were higher than in the control group. These were not statistically significant for myeloperoxidase and malondialdehyde. Also, our histopathologic results indicated that ethanol administration increased pancreatic tissue injury. Gallic acid especially at 200?mg/kg improved ethanol-mediated pancreatic tissue damage.In conclusion, gallic acid treatments were decreased release of lysosomal cathepsin B and L enzymes into cytoplasmic fraction and prevented alcohol mediated pancreatic tissue injury. Preventive effect of gallic acid might be dose-dependent.     

白藜芦醇联合乌司他丁治疗急性胰腺炎的疗效分析

目的：观察白藜芦醇联合乌司他丁对大鼠急性胰腺炎（AP）的治疗效果。方法：将250只雄性Wister大鼠随机分为5组,分别为假手术（A）组、急性胰腺炎组（B组）、白藜芦醇组（C组）、乌司他丁组（D组）和白藜芦醇联合乌司他丁治疗组（C＋D组）。制备各组AS大鼠模型,观察各组腹水量及血淀粉酶、脂肪酶、TNF-α、NF—κB、丙二醛（MDA）及超氧化物歧化酶（SOD）水平,并观察胰腺病理改变。结果：B组与A组相比,SOD水平明显降低（P〈0．05）,MDA水平明显升高（P〈0．05）;C、D及C＋D组与B组相比,血清SOD水平明显升高（P〈0．05）,MDA水平明显降低（P〈0．05）;C＋D组与C组、D组相比,血清SOD水平明显升高（P〈O．05）,血清MDA水平明显降低（P〈0．05）。与B组比较,C和D组血淀粉酶、脂肪酶、TNF-α、病理学评分均降低,细胞超微结构损伤减轻,有显著性差异（P〈0．05或P〈0．01）。C＋D组上述指标改善较C组和D组更明显,差异有显著性（P〈0．05）。结论：乌司他丁、白藜芦醇通过升高SOD保护性因子、降低MDA损伤性因子,对急性胰腺炎有治疗作用,尤其在乌司他丁与白藜芦醇合用时效果更显著。     

Influence of delta-sleep-inducing peptide on the activity of proteolytic enzymes in the rat brain under hypokinesia]

Single administration of the delta-sleep-inducing peptide (DSIP) in a dose of 12 micrograms/100 g to intact animals makes the activity of neutral proteinases and cathepsin D higher in the rat brain and blood serum. Hypokinesia of different duration changes activity of neutral and acidic proteinases and induces accessibility of cathepsin D to the cytosol as a result of damage in lysosomal membrane. Injection DSIP induces a decrease A/B of cathepsin D to the control level under 1-h hypokinesia condition and normalizes the neutral proteolytic activity under 6-h hypokinesia condition.     

Localization of lysosomal and digestive enzymes in cytoplasmic vacuoles in caerulein-pancreatitis

Intracellular localization and enzymatic activities of lysosomal enzymes (cathepsin B, N-acetyl-beta-glucosaminidase, and beta-glucuronidase) were studied in control rats and after induction of caerulein pancreatitis. In control rats high enzymatic activities were found in the postnuclear 1000 g fraction (purified zymogen granules). The corresponding subcellular fraction in pancreatitis animals additionally contained larger secretory vacuoles and autophagosomes and revealed a marked increase in lysosomal enzyme activities. Immunolabelling studies at the ultrastructural level for trypsinogen and cathepsin B demonstrated a colocalization of lysosomal and digestive enzymes in zymogen granules in healthy controls. After induction of pancreatitis immunolabelling still demonstrated a colocalisation of cathepsin B and trypsinogen in secretory granules and newly formed Golgi-derived secretory vacuoles. Concomitantly appearing autophagosomes were, however, only labelled for cathepsin B. It is concluded that segregation of lysosomal and digestive enzymes is incomplete in normal acinar cells resulting in a colocalization in zymogen granules. In pancreatitis colocalization in secretory granules is maintained, whereas only lysosomal enzymes were sufficiently transferred into autophagic vacuoles. No indication for impaired mechanisms of molecular sorting of lysosomal and digestive enzymes in caerulein-induced pancreatitis was found.     

Activity of cathepsin B,D and L in rat cerebrum after cimetidine and famotidine administration

Cathepsins are lysosomal enzymes that are used a sensitive markers in various toxicological investigations. The purpose of this study was to evaluate and compare the influence of cimetidine and famotidine on the cerebral cortex, particularly on the activity of cortical cathepsin B, D and L in the frontal lobe of rat brain. The drugs were administered intraperitoneally, twice a day, for six weeks to male Wistar rats in two doses. The initial dose was 2.85 mg/kg for cimetidine and 0.285 mg/kg for famotidine. The second dose was 10 times higher. Control animals were injected with 0.9% NaCl. Half of the animals from each of the drug-treated and control groups were sacrificed on the 42nd day of the experiment. The remaining animals were raised for another 6 weeks without any xenobiotics, and sacrificed on the 84th day. The frontal lobe of the right cerebral hemisphere was taken for biochemical investigation. The activities of free and bound fractions of cathepsin B, D and L were evaluated spectrophotometrically in cortical homogenates. The activity of bound fraction of cathepsin D and L decreased significantly in animals exposed to the higher dose of cimetidine and sacrificed on the 42nd day. Also significant elevation of the free fraction of cathepsin L was noted in the same group of rats. Cathepsin activities were normalized during the next six weeks. No behavioural changes were noted among the observed animals. Unlike cimetidine, famotidine did not change profiles of the cerebral cathepsins.     

The effect of hyperbaric oxygen treatment on oxidative stress in experimental acute necrotizing pancreatitis

Various protocols may be used for acute pancreatitis treatment. Recently, the benefit of hyperbaric oxygen (HBO) has been demonstrated. To clarify the mechanism of HBO on the process of the acute pancreatitis, we determined the levels of antioxidant enzymes in an acute pancreatitis model. Forty-five Sprague-Dawley rats were randomly divided into three groups: Group I: sham group (n=15), Group II: pancreatitis group (n=15), Group III: pancreatitis group undergoing HBO therapy (n=15). HBO was applied postoperatively for 5 days, two sessions per day at 2.5 fold absolute atmospheric pressure (ATA) for 90 min. Superoxide dismutase (Cu/Zn-SOD), malondialdehyde (MDA), and glutathione peroxidase (GSH Px) activity were measured in pancreatic tissue and erythrocyte lysate. MDA and GSH Px were also determined in plasma. In addition, amylase levels were measured in the serum. While serum amylase levels and MDA values in erythrocyte, plasma and pancreatic tissue were decreased, the levels of GSH Px and SOD were found to be significantly increased in the Group III as compared to those of the Group II. The findings of our study suggest that HBO has beneficial effects on the course of acute pancreatitis and this effect may occur through the antioxidant systems.     

Activity of Ligustrum vulgare L extracts against acute pancreatitis in murine models by regulation of p38 MAPK and NF-κB signaling pathways

Pancreatitis is a fatal disease associated with significant mortality and morbidity. At present, no specific treatment is available for pancreatitis and the patients are mainly treated with supportive medication. The need for specific antipancreatitic chemotherapy is an urgent medical obligation. In the current study, protective effects of the methanolic extract of the Ligustrum vulgare berries were investigated in the rat model of acute pancreatitis. Acute pancreatitis (AP) was induced in the male Sprague-Dawley (SD) rats by cerulein injection. Fruit extract of L. vulgare L extract was prepared using the methanol. Treatment effects of L. vulgare were evaluated in AP rats. Serum levels of lipase, amylase, proinflamatory cytokines (TNF-α, IL-6, TL-1β), lipid peroxidase (LPO), myeloperoxidase (MPO) were determined. Histological changes in the pancreas were assessed. L. vulgare treatment prevented the increase in serum amylase and lipase levels, reduced the disease progression in pancreas, and reduced the serum levels of tumour necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1β in AP rats. Moreover, L. vulgare significantly suppressed pancreatic edema, inhibited oxidative damage (MPO activity and SOD activity), and inhibited the expression of NF-κB/p65 and activation (phosphorylation) of the inhibitor of NF-κB (IκBα) and p38 MAPKs. Histological examinations showed that L. vulgare significantly reduced the inflammatory and fibrotic changes. The results indicated the potent pancreato-protective effects of L. vulgare in AP.     

Primary sensory neurons: a common final pathway for inflammation in experimental pancreatitis in rats

We hypothesized that neurogenic inflammation is a common final pathway for parenchymal inflammation in pancreatitis and evaluated the role of primary sensory neurons in secretagogue-induced and obstructive pancreatitis. Neonatal rats received either the primary sensory neuron-denervating agent capsaicin (50 mg/kg s.c.) or vehicle. At 8 wk of age, pancreatitis was produced by six hourly injections of caerulein (50 microg/kg i.p.) or by common pancreaticobiliary duct ligation (CPBDL). The severity of pancreatitis was assessed by serum amylase, pancreatic myeloperoxidase (MPO) activity, histological grading, pancreatic plasma extravasation, and wet-to-dry weight ratio. Caerulein significantly increased MPO activity and wet-to-dry weight ratio, produced histological evidence of edematous pancreatitis, induced plasma extravasation, and caused hyperamylasemia. CPBDL increased MPO activity and produced histological evidence of pancreatitis. Neonatal capsaicin administration significantly reduced tissue MPO levels, histological severity scores, and wet-to-dry weight ratio and abolished plasma extravasation. These results demonstrate that primary sensory neurons play a significant role in the inflammatory cascade in experimental pancreatitis and appear to constitute a common final pathway for pancreatic parenchymal inflammation.     

清胰汤对大鼠急性坏死性胰腺炎IL-6,IL-10及肠道通透性影响

目的：探讨清胰汤改善大鼠急性坏死性胰腺炎（acute necrotizing pancreatitis）ANP炎症反应及肠道通透性功能的治疗效果及机制。方法：将72只雄性SD大鼠随机分为3组,其中2组大鼠采用从胰腺被膜下多点缓慢均匀注入3.8%牛黄胆酸钠（0.5ml/100g）建立大鼠急性坏死性胰腺炎模型,再分为急性坏死性胰腺炎常规治疗组（A组）、清胰汤干预治疗组（B组）,其他24只大鼠为假手术组（S组）,每组再随机分为24h、48h、72h组。各组于12h后给于肠内营养,B组肠内营养后给于2次清胰汤2.5ml/100g,A组、S组给于同等剂量生理盐水。各组于建模后24h、48h、72h处死,腹腔动脉取血检测血清淀粉酶浓度、IL-6、IL-10、D-乳酸水平。结果：48h时点B组IL-10水平较A组高（P〈0.05）;72时点B组血清淀粉酶水平较A组低（P〈0.01）,IL-6水平较A组低（P〈0.01）,IL-10水平较A组高（P〈0.01）,D-乳酸水平较A组低（P〈0.01）。结论：清胰汤可以上调IL-10改善大鼠急性胰腺炎炎症反应从而降低肠道通透性。     

The role of nuclear factor‐κB in rats of radiocontrast‐media‐induced nephropathy

This study was undertaken to examine the possible role of the DNA‐binding activity of nuclear factor‐kappa B (NF‐κB) in rat of radiocontrast‐media‐induced nephropathy (RCIN) and to explore the characteristic of RCIN in rats and the role of NF‐κB in its occurrence. Forty‐eight adult male Sprague–Dawley (SD) rats were randomly divided into Groups A–D. Rats of Groups A and B were intravenously injected with NG‐nitro‐L ‐arginine methyl ester (L‐NAME) (10 mg/kg) and indomethacin (10 mg/kg), respectively. Rats of Groups C and D were intravenously injected with 1‐M phosphate buffer (PH = 8.4 3 mL/kg) and normal saline (NS 2 mL/kg), respectively. After 30 min, Groups A and D were injected with NS (8 mL/kg) and Groups B and C were injected with diatrizoate (DTZ 8 mL/kg). After injected contrast media (CM) for 6 h, the serum creatinine and blood urea nitrogen of rat in Group B increased sharply as compared with Groups A, C, and D. After 48 h, the data recovered to 49.28 ± 8.81 μmol/L and 6.72 ± 2.75 mmol/L, respectively. Vacuolization of the tubule epithelial cells of the kidney was observed in Group A. Especially, these pathological changes were most obvious in outer medulla. Contrast to group A, the DNA‐binding activity of NF‐κB in rat kidney of Group B reached a peak at the 6th h and recovered to the normal level after the 48th h. CM mainly damages renal tubular–interstitial, which appears the earliest and most serious in the outer medulla. Activation of NF‐κB of renal may be one of the mechanisms of RCIN occurrence. © 2008 Wiley Periodicals, Inc. J Biochem Mol Toxicol 22:416–421, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20256     

乳酸杆菌对实验性急性胰腺炎损伤的治疗价值

目的探讨乳酸杆菌对急性胰腺炎的治疗作用。方法采用家兔急性胰腺炎模型,其中实验组给予乳酸杆菌干预,检测实验组、对照组血清淀粉酶、血清钙和血糖3项指标。结果实验组血清淀粉酶水平低于对照组(P<0.01)。结论乳酸杆菌对实验性急性胰腺损伤有修复作用。     

大鼠胰腺炎相关性急性肺损伤模型的探讨

目的研究5%牛磺胆酸钠(TAC)逆行胆胰管注射诱发急性胰腺炎相关肺损伤的大鼠模型。方法采用改进的胆胰管逆行注射TAC造成大鼠急性出血坏死型胰腺炎(AHNP)模型,将大鼠随机分为3组:AHNP组、假手术组、地塞米松(DXM)治疗组。造模成功后,立即静脉注射大剂量DXM(5 mg/kg)。术后于3、6、12 h处死,留取外周血测定血清淀粉酶、脂肪酶,取右肺中叶测定肺湿干比值及作病理切片,计算等级评分评价肺损伤;行支气管肺泡灌洗,以灌洗液白蛋白与血清白蛋白含量比值计算肺指数。结果AHNP组36、、12 h肺通透性指数、湿干比值及病理学评分逐渐增加,经单因素方差分析,61、2 h组高于3 h组(P<0.05),前两者于6、12 h组组内比较差异不显著(P>0.05)。DXM组于术后61、2 h,各项肺损伤指标均低于AHNP组(P<0.05)。结论TAC胆胰管逆行注射造成AHNP模型大鼠于术后6 h即出现明显的肺损伤表现,符合PALI病理改变,与临床AHNP合并急性肺损伤(ALI)的病理过程相似,可于此时相点作为研究AHNP合并肺损伤的模型。     

Inhibitions of degradation of rat liver aldolase and lactic dehydrogenase by N-[N-(L-3-trans-carboxyoxirane-2-carbonyl)-L-leucyl]agmatine or leupeptin in vivo

When injected into rats, leupeptin and E-64 (N-[N-(L-3-trans-carboxyoxirane-2-carbonyl)-L-leucyl]agmatine), potent thiol protease inhibitors of microbial origin, inhibited cathepsin B (EC 3.4.22.1) and cathepsin L (EC 3.4.22.-) in the lysosomal fraction of liver. Both compounds strongly inhibited cathepsin B, but E-64 had more effect than leupeptin on cathepsin L. Neither compound inhibited cathepsin D (EC 3.4.23. 5). E-64 reduced the apparent turnover rate of aldolase (EC 4. 1.2.13) markedly and the turnover rates of lactic dehydrogenase (EC 1.1.1.27) and total soluble protein slightly. Leupeptin had apparently less effect on degradation of those enzymes, but significant effect on degradation of aldolase. These results indicate that proteinases, which are sensitive to inhibition by E-64 or leupeptin, especially cathepsin L and cathepsin B may be important in degradation of aldolase.     

急性胰腺炎大鼠腺泡细胞凋亡及X连锁凋亡抑制蛋白XIP的表达

目的:研究急性胰腺炎(AP)大鼠腺泡细胞凋亡,X连锁凋亡抑制蛋白(XIAP)的表达及其与疾病严重程度的关系。方法:通过胰胆管逆行注射不同浓度的牛黄胆酸钠,制备急性水肿型胰腺炎(AEP)和急性坏死性胰腺炎(ANP)大鼠模型,同时设假手术(SO)组为对照。收集各模型组3,6和12h标本,对胰腺组织进行病理学评分,并测定血清淀粉酶和腹水量;用TUNEL染色检测胰腺腺泡细胞的凋亡,分别RT-PCR和Western Blotting法测定大鼠胰腺组织XIAP mRNA及蛋白的表达。结果:成功建立了大鼠AP模型。同SO组相比,ANP和AEP组胰腺组织在各时间点均有不同程度的病理损害,血清淀粉酶也显著增高(P均<0.01)。且ANP组显著高于AEP组(P均<0.01)。造模成功3h后,各组大鼠胰腺腺泡细胞均出现少量凋亡,但ANP和AEP组凋亡显著多于SO组(P<0.05),ANP和AEP组间没有差别(P>0.05)。同SO组相比,ANP和AEP组在6h和12h时凋亡均增多(P<0.01),且AEP组显著高于ANP组(P<0.01)。造模成功3h后,各模型组XIAP mRNA表达没有差异(P>0.05);6h和12h时AEP组XIAP mRNA表达明显下降,而ANP组明显升高,两组间差异有显著性(P<0.01)。XIAP蛋白表达水平与mRNA表达水平相一致。结论:急性胰腺炎大鼠胰腺组织XIAP表达与腺泡细胞凋亡情况相反,且与疾病严重程度平行。XIAP可能负性调控AP大鼠胰腺腺泡细胞的凋亡。     

Purification and tissue distribution of rat cathepsin L

Cathepsin L was purified to apparent homogeneity from rat kidney. The molecular weight of the enzyme was estimated to be 30,000, but part of the enzyme was found to consist of two polypeptide chains of Mr 25,000 and 5,000. Antibody against rat kidney cathepsin L did not cross-react with rat cathepsin B or H and detected only cathepsin L in crude rat tissue preparations on immunoblotted sheets. The concentrations of cathepsin L in various rat tissues and peripheral blood cells of rats were determined by a sensitive immunoassay, in which the minimum detectable amount of cathepsin L was 20 pg/assay. The concentration of cathepsin L was found to be highest in the kidneys, where it was more than 3 times higher than in the liver, spleen, lungs, and brain. Nervous tissues, especially the cerebellar cortex, also contained fairly high concentrations of cathepsin L, but the heart, skeletal muscle, and gastrointestinal tract contained low concentrations, as did peripheral blood cells. The cathepsin L content of macrophages was 20% of that of cathepsin B. The concentrations of cathepsin L in lymphocytes, neutrophils, and erythrocytes were 10%, 20%, and less than 0.2%, respectively, of those in resident macrophages.