Lysosomal Acid Hydrolase Activities Research Articles

Hereditary β-mannosidosis in a dog: Clinicopathological and molecular genetic characterization

Hereditary β-mannosidosis causing progressive lysosomal neuropathy and other clinical signs, has been previously described in humans, Nubian goats, and Salers cattle. Here we report the clinicopathological, metabolic, and molecular genetic features of canine beta-mannosidase (MANBA, EC 3.2.1.25) deficiency. A 1-year-old male mix-breed dog from St. Kitts was presented with progressive stumbling, weakness, and regurgitation. Vacuolated lymphocytes were observed on the blood film. Postmortem findings included marked enlargement of nerves, megaesophagus, and internal hydrocephalus. Vacuolated macrophages, neurons, and secretory epithelial cells suggested an oligosaccharide storage disease. Plasma concentration of the β-mannosidosis specific oligosaccharide was approximately 75 fold that of controls. The plasma beta-mannosidase activity was severely reduced to ~5% of controls; five other lysosomal acid hydrolase activities were increased or within their normal reference interval. Genomic sequencing of this dog's MANBA gene identified a homozygous exonic five bp tandem duplication in the penultimate exon of the MANBA gene (c.2377_2381dupTATCA) which results in a reading frame shift, altering the subsequent amino acid sequence and creating a premature stop codon. The truncated beta-mannosidase enzyme is expected to be dysfunctional. This enzyme deficiency causes the accumulation of un-degraded oligosaccharides in cells, which affect the myelination of the peripheral and central nervous systems. This insertion was not encountered in 121 and 80-screened samples from dogs on St. Kitts (all were homozygous for wild-type) and Philadelphia region (wild-type), respectively. In conclusion, canine β-mannosidosis has similar clinicopathological features with some human patients, but milder signs than in ruminants and more severe than in knockout mice. Hence, dogs with β-mannosidosis could become a valuable disease model for the human disease.

Altered regulation of serum lysosomal acid hydrolase activities in Parkinson's disease: A potential peripheral biomarker?

IntroductionRecent studies have indicated that lysosomal dysfunction contributes to the development of idiopathic Parkinson's disease (PD). It is uncertain whether dysregulation of serum lysosomal acid hydrolase activity exists in sporadic PD patients compared with normal controls (NCs) and parkinsonian syndrome (PS) patients. MethodsSporadic PD patients without GBA1 mutations (n = 68) were matched with normal controls (n = 45), and parkinsonian syndrome patients (n = 32) in terms of family history, age, and sex. We measured the activities of lysosomal enzymes, α-galactosidase, β-galactosidase, and β-hexosaminidase and examined the possible correlations between lysosomal acid hydrolase activities with age in NCs, PD, and PS patients. Resultsβ-Galactosidase activity was significantly higher in the PD and PS than in the NC group (P < 0.001). The β-galactosidase to α-galactosidase and β-hexosaminidase to β-galactosidase activity ratios were more useful for distinguishing PD and PS patients from NCs (P < 0.0001). Furthermore, α-galactosidase activity was significantly higher in PS patients than both PD and NC groups (p = 0.04). β-Galactosidase and α-galactosidase activities exhibited a statistically significant negative correlation with age in NCs, and β-hexosaminidase activity showed a positive correlation with age in PS. However, PD patients did not show any of these correlations. ConclusionOur results suggest the presence of an unknown regulatory mechanism(s) of serum acid hydrolase activities with aging in the normal population and abnormalities in their regulation in PD and PS patients. However, the pattern of dysregulation in these two groups is different. Thus, serum lysosomal acid hydrolase activity can be used as a peripheral biomarker for PD.

Protective effect of lupeol and lupeol linoleate in hypercholesterolemia associated renal damage

The association between hypercholesterolemia and kidney damage has been well known for last few decades. The oxidative stress and inflammatory responses are involved in renal injury, which is upregulated in hypercholesterolemic condition. The present study is aimed to evaluate the possible effect of lupeol and its ester derivative, lupeol linoleate in renal damage associated with hypercholesterolemic rats. Hypercholesterolemia was induced in male Wistar rats by feeding them with a high cholesterol diet (HCD) comprising normal rat chow supplemented with 4% cholesterol and 1% cholic acid for 30 days. Lupeol and lupeol linoleate were supplemented (50 mg/kg body wt/day) to HCD fed rats during the last 15 days. Increased levels of renal total cholesterol, triglycerides and phospholipids, along with altered serum biochemical parameters of tissue injury indices and elevated activities of renal marker enzymes (lactate dehydrogenase and alkaline phosphatase) were noted in HCD fed rats. Elevated lipid peroxidation levels coupled with decreased antioxidant status (enzymatic and non enzymatic antioxidants) were observed in hypercholesterolemic rats, which indicate the onset of oxidative changes in the renal tissue. Renal lysosomal acid hydrolase activities (ACP, beta-Glu, beta-Gal, NAG and Cat-D) and acute phase proteins like C-Reactive protein and fibrinogen were significantly increased in HCD fed rats, which further indicates the heightening of inflammation. In addition, histopathological findings also confirmed the renal damage in hypercholesterolemic condition. Lupeol and lupeol linoleate effectively reverted the above abnormalities and was comparable with that of the control. These observations highlight the protective effect of lupeol and its ester derivative in ameliorating the renal injury associated with hypercholesterolemia.

Effect of dl-α-lipoic acid on cyclophosphamide induced lysosomal changes in oxidative cardiotoxicity

Cyclophosphamide (CP), one of the widely prescribed antineoplastic drugs can cause fatal cardiotoxicity. The present study is aimed at evaluating the cardioprotective role of lipoic acid in CP induced toxicity. Male albino rats of Wistar strain were divided into four groups and treated as follows: Group I served as control, Group II received a single dose of CP (200 mg/kg b.wt., i.p.), Group III received lipoic acid (25 mg/kg b.wt., orally) for 10 days, and Group IV received CP immediately followed by lipoic acid for 10 days. In CP administered rats, the levels of protein carbonyl and 8-hydroxy-2-deoxyguanosine were increased significantly ( P < 0.001) indicating oxidative changes in the heart tissue. The activities of lysosomal acid hydrolases, β-Glu, β-Gal, NAG, Cat-D and ACP increased significantly ( P < 0.001) in the serum as well as in the heart tissue after CP administration. An increase in hydroxyproline was observed in CP induced rats. Lipoic acid effectively reverted these abnormal biochemical changes to near normalcy. These observations highlight the protective role of lipoic acid in CP induced cardiotoxicity.

Increased activity of lysosomal acid hydrolases in the cell-free cerebrospinal fluid of bacterial meningitis.

Because inflammation could affect lysosomal enzyme trafficking, resulting in increased enzyme release from the cells, tissue necrosis, or altered blood- and the brain-cerebrospinal fluid (CSF) barrier, the activity of four lysosomal enzymes in the cell-free CSF of 34 patients with bacterial meningitis, 20 with aseptic meningitis, and 39 control subjects was measured. Activities are expressed in nanomoles of 4-methylumbelliferone mL/h. The median beta-hexosaminidase A activity in bacterial meningitis was 313, in aseptic meningitis it was 173, and in the control subjects it was 175, the median beta-hexosaminidase B activity was 417, 165, and 120; the median alpha-mannosidase activity was 171, 124, and 113; and the median beta-glucuronidase activity was 133.7, 14.3, and 10.0, respectively. The difference of the activities of the four enzymes measured between the bacteria meningitis and the controls is significant (p < 0.000). Also significant is the difference between bacterial and aseptic meningitis (p = 0.005 to < 0.000), but it is not significant between aseptic and control subjects. Both the sensitivity and specificity of the beta-glucuronidase activity between bacterial meningitis and control subjects were 100%, whereas the corresponding values between bacterial and aseptic meningitis were 100% and 90%, respectively. No significant correlation was observed between the activities of the enzymes measured and the number of the polymorphonuclear leukocytes or other laboratory characteristics of the CSF. The increased lysosomal enzyme activities in the CSF of patients with meningitis may result from diffusion across the blood-CSF or the brain-CSF barrier or from enzyme leakage through the cell membranes.

Biosynthesis, processing, and secretion of α-L-fucosidase in lymphoid cells from patients with I-cell disease and pseudo-Hurler polydystrophy

N-Acetylglucosamine 1-phosphotransferase is a key enzyme required for synthesis of the mannose 6-phosphate recognition marker that is used by many newly made acid hydrolases for their transport to lysosomes. It has previously been found that lymphoid cells from patients with I-cell disease and pseudo-Hurler polydystrophy have nearly normal intracellular and intralysosomal activities of several lysosomal acid hydrolases, despite a deficiency of N-acetylglucosamine 1-phosphotransferase. These results suggest that lymphoid cells may provide an important system to investigate alternate mechanisms for targeting newly made acid hydrolases to lysosomes. In the present study, the biosynthesis, processing and secretion of alpha-L-fucosidase in I-cell and pseudo-Hurler lymphoid cells was used as a model system to study the existence of such mechanisms. The level of intracellular alpha-L-fucosidase protein in exponentially growing I-cell or pseudo-Hurler lymphoid cultures was statistically indistinguishable from the mean of 19 control cultures. A 1.5 h [35S]methionine pulse experiment showed that alpha-L-fucosidase is initially synthesized by I-cell, pseudo-Hurler and control cultures as an intracellular form (Mr = 58,000). Companion cultures chased with methionine from 2 to 21 h processed the enzyme to an intracellular form (Mr = 60,000) and an extracellular form (Mr = 62,000). All enzyme forms were glycoproteins with polypeptide chains of Mr 52,000. In control cells incubated with radioactive inorganic phosphate (32Pi), less than 1% of the 32Pi incorporated into alpha-L-fucosidase was associated with carbohydrate chains and greater than 99% with polypeptide chains. In I-cell disease lymphoid cells, the 32Pi incorporated into alpha-L-fucosidase was associated solely with polypeptide chains. A qualitative analysis of phosphorylated residues identified phosphoserine in alpha-L-fucosidase from control and I-cell lymphoid cells. Only alpha-L-fucosidase from control cells contained mannose 6-phosphate. These results are consistent with the proposal that I-cell lymphoid cells may use a mannose 6-phosphate-independent mechanism for routing alpha-L-fucosidase. Additional metabolic labelling experiments demonstrated the presence of 32P-labelled alpha-L-fucosidase in both cells and medium of a control lymphoid culture, but only in cells of an I-cell lymphoid culture. In contrast, alpha-L-fucosidase labelled with [35S]methionine was found in cells and medium of control and I-cell lymphoid cultures. Since phosphoserine was only found to occur in intracellular, but not in extracellular alpha-L-fucosidase of the I-cell culture, we speculate that phosphoserine may be involved in intracellular retention of alpha-L-fucosidase in I-cell lymphoid cells.

Proteolytic enzyme activity in rat hindlimb muscles in fetus and during post-natal development.

The enzymatic activity of two lysosomal enzymes, acid phosphatase and cathepsin D, was determined in fetus and during post-natal development of the rat gastrocnemius muscle in comparison to the histological differentiation of this muscle. The specific activity of cathepsin D and acid phosphatase was 7 and 2.5 fold higher in the muscle during development until 20 days after birth, than that of mature muscle, respectively. A trend of gradual decrease in the activity of these enzymes was observed concomitantly with the differentiation and maturation of the muscle from mononucleated cells in the fetus to myotubes formation at day 1 after birth, followed by the formation of "young" and then striated myofibers in 10- and 20-day old neonates, respectively. However, no correlation could be found between the lysosomal enzyme activity and the developmental stages of the muscle until 20 days after birth. It is suggested that the elevated activity of lysosomal acid hydrolases may be associated with late developmental processes from young to mature myofibers in normal skeletal muscle and not only in various pathological conditions.

Seasonal cycle of lysosomal enzyme activities in the mantle tissue and isolated cells from the musselMytilus edulis

InMytilus edulis L., gametogenesis takes place in the mantle at the expense of the connective storage tissue. There are two main types of storage cells: vesicular (VC) cells storing large amounts of glycogen and adipogranular (ADG) cells containing large numbers of protein granules, lipid droplets and lesser amounts of glycogen. One of the ways in which stored reserves can be mobilized for gamete formation is by controlled autophagy, in which the cellular constituents are degraded by lysosomes. Mussels were collected from the Menai Strait, North Wales, and monthly measurements made, over two years (1984–1986), of the activities of lysosomal acid hydrolases (acid phosphatase,β-N-acetyl-D-glucosaminidase andβ-glucuronidase) and Cathepsins B and L in the mantle tissue, isolated ADG cells, low-density cells and, during spawning, in the mature oocytes of female mussels. The lysosomal proteinases, Cathepsins B, L and H, were further characterised by activation with thiol compounds and inhibition with thiol blockers and by leupeptin. Because of the low activity in the mantle tissue ofM. edulis, Cathepsin H was not assayed on a seasonal basis. There was a general increase in lysosomal enzyme activity during the winter, which can be related to increased autolysis in the storage cells and to the process of maturation in the developing oocytes. The activity of Cathepsin B was highest in the ADG and low-density cells, implying an important role in proteolysis within the ADG cells. By contrast, Cathepsin L displayed the highest activity in the mature oocytes, suggesting a major function of Cathepsin L in the development and maturation of the oocytes. Two differentα-glucosidase activities were measured in the monthly assays, one with a pH optimum of 4.5 (acid) and the other at pH 7.5 (neutral). Highest activities of the acidα-glycosidase were found in the low-density cells, but there were no significant seasonal changes in the mantle tissue as a whole. Activities of the neutralα-glucosidase were low in the ADG cells and mature oocytes, but showed high activities in the mantle tissue, with marked seasonal changes that corresponded to the mobilization of glycogen reserves in the VC cells.

Effect of dibutyryl cyclic AMP and theophylline on lipoprotein lipase secretion by human monocyte-derived macrophages

The effect of dibutyryl cyclic AMP and theophylline on lipoprotein lipase secretion was investigated after a 24 h pretreatment of human monocyte-derived macrophages. Both the effectors decreased in a dose-dependent manner the enzyme activity recovered in the culture medium. The decrease in lipoprotein lipase activity appeared to be related to reduced enzyme synthesis without apparent modification of its stability and half-life and was conversely associated with an increase of lysosomal acid hydrolase activities. This effect was reversible on removal of the nucleotide. The present findings suggest that cyclic AMP may play a role in lipoprotein lipase expression in human macrophages and therefore may participate in the regulation of lipoprotein uptake by these cells, which are strongly implicated in the atherogenic process.

Arterial prostaglandins and lysosomal function during atherogenesis: II. Isolated Cells of Diet-Induced Atherosclerotic Aortas of Rabbit

This report validates and expands further the interpretation of our findings on prostaglandins and lysosomes in rabbit aortic homogenates (see paper 1 of this series) to enzymatically isolated and separated aortic cell populations during atherogenesis. Evidence is provided by which isolated arterial cells may be considered representative of in situ increases of diseased aortic tissue prostaglandin I 2 and E 2 levels, as well as lysosomal acid hydrolase activities and total cholesterol content based on DNA. Increasing latency of aortic lysosomal N-acetyl-β-glucosaminidase activity was confirmed and correlated with increasing severity of atherosclerosis, in parallel to increasing levels of prostaglandin I 2 but not increasing levels of prostaglandin E 2. Ultrastructural observations also confirmed aortic intracellular lipid accumulation within lysosomes and as lipid droplets. Consistent with these relationships, separated low density, lipid-filled aortic cells were especially increased in total (197%) and latent (15%) lysosomal acid hydrolase activities, catalase activity (274%), total cholesterol (151%), and in both prostaglandin I 2 (67%) and E 2 (325%) levels based on DNA, as compared to control aortic cells or more normal-appearing high-density diseased aortic smooth muscle cells; high-density diseased aortic cells were increased in prostaglandin E 2 but similar in latent acid hydrolase activity compared to control aortic cells. Since the total cholesterol content of rabbit atherosclerotic aortas was evidenced more intracellularly (75%) than extracellularly (25%) in this study, the association of increased prostaglandin I 2 and E 2 levels with low-density lipid-filled cells suggest the participation of these prostaglandins in the genesis of aortic foam cells during arterial lipid accumulation in rabbit atherosclerosis. The association of increasing prostaglandin I 2 levels and increasing latent lysosomal N-acetyl-β-glucosaminidase activities also implicates a possible relationship between this prostaglandin and lysosomal membranes of aortic cells, either primary or secondary to intralysosomal lipid accumulation.

Increase in the activity of lysosomal acid hydrolases in the chondrocytes of arthritic joints of rabbits with experimental allergic arthritis.

Undecalcified cryostat sections of the cartilage-covered ends of the femurs have been prepared from the control and inflamed knees of rabbits with experimental allergic arthritis. The activities of two lysosomal hydrolases, naphthylamidase and beta-glucuronidase, were assayed in the chondrocytes of the articular cartilage in such sections by scanning and integrating microdensitometry. The activities of both enzymes were found to increase significantly in the chondrocytes of the inflamed joints.

A comparison of lysosomal acid hydrolase activities in human gastric antrum and in different regions of the porcine stomach

1. 1. Lysosomes are known to be implicated in many disease states in both humans and animals. 2. 2. In order to assess the possible role of lysosomes in the aetiology of human gastric ulceration, lysosomal enzyme levels and some of their properties were determined in human gastric antrum and in three discrete porcine gastric regions. 3. 3. Of the four regions investigated, the strongest similarity emerged between the enzymes of the porcine pyloric gland area and those of the human antrum. 4. 4. These data suggest that the pyloric gland is an appropriate model tissue for a comparative in vitro study of lysosomal involvement in human gastric ulceration.

Serum lysosomal acid hydrolase activities in Graves' disease

The activities of seven lysosomal enzymes (α- d-glucosidase, β- d-galactosidase, β- d-glucuronidase, hexosaminidase, α- l-fucosidase, α- d-mannosidase, acid phosphatases) were studied in the serum of 31 untreated patients with Graves' disease, 30 treated hyperthyroid patients whose clinical abnormalities had disappeared and whose hormones had returned to euthyroid levels, and 34 controls. The hyperthyroid state is characterized by increased serum levels of α- d-glucosidase, β- d-glucuronidase, hexosaminidase and especially of α- l-glucosidase and α- d-mannosidase. In contrast, neither β- d-galactosidase nor acid phosphatases serum levels were significantly modified. After antithyroid treatment, the activities of these enzymes returned to normal levels, except for α- d-mannosidase. The interpretation of these changes in serum acid hydrolases activities is controversial.

Changes of dipeptidyl aminopeptidase activities in mouse skeletal muscle following prolonged running

1. 1. The activities of dipeptidyl aminopeptidases (DAP), leucine arylamidase and β-glucuronidase were assayed in red and white parts of mouse quadriceps femoris muscle 3 and 7 days after a single bout of prolonged running. 2. 2. The activities of lysosomal acid hydrolases (DAP I, DAP II and β-glucuronidase) were highly increased on the 3rd day after the exertion and then decreased by the 7th day. The response was more prominent in red than in white skeletal muscle. 3. 3. The activities of two microsomal hydrolases, DAP IV and leucine arylamidase, increased much less than those of the lysosomal acid hydrolases. The highest activities were recorded on the 7th day after exertion. 4. 4. The activity of DAP III, a cytoplasmic peptidase, was unaffected in red muscle but slightly increased in white muscle. 5. 5. The protein content of red skeletal muscle, but not that of white muscle, decreased transiently after the running. 6. 6. It seems that strenuous exercise selectively stimulates the lysosomal proteolytic system in skeletal muscle, while the others are less affected.

Biochemical activities of lysosomal acid hydrolases in leukemic cells

The biochemical activities of 8 lysosomal acid hydrolases in leukemic cells from 48 patients were examined. Characteristic alterations were found in α-mannosidase, β-galactosidase and N-acetyl- β-glucosaminidase activities of leukemic cells. The level of α-mannosidase activity was much higher in myelo(mono)genous leukemias (AML, AMoL, AMMoL, CML and CMMoL) than in lymphogenous ones (ALL, T-cell leukemia, hairy cell leukemia and CLL) without exception. The β-galactosidase activity also differed as a result of α-mannosidase, except in T-cell leukemia. In T-cell leukemia it was within the range of normal lymphocytes, but in the other lymphogenous leukemias it was significantly below normal. N-acetyl- β-glucosaminidase activity in myelo(mono)genous leukemic cells was above the range of normal granulocytes. The changes in these enzyme levels were consistent. The lymphocytic or myelocytic nature of three cases of acute undifferentiated leukemia could be determined by enzyme studies. In two cases it was lymphocytic and in one it was myelocytic. The enzymatic abnormalities were also found in morphologically mature neutrophils from patients with not only chronic types (CML, CMMoL) but also acute types (AMoL, AMMoL) of leukemias, and were similar to those of their respective leukemic cells. Analysis of lysosomal enzymes (at least three of those mentioned above), can elucidate one of the biochemical properties of leukemic cells and may be valuable in the differentiation of leukemias.

Prenatal diagnosis of I-cell disease by measuring altered alpha-mannosidase activity in amniotic fluid.

Prenatal diagnoses of I-cell disease were carried out by examination of the amniotic fluid and cultured amniotic cells in four cases of high-risk pregnancy in three different families. Three of the four fetuses were diagnosed as having I-cell disease, on the basis of observation of abnormally increased activity of lysosomal acid hydrolases in the amniotic fluid and their decreased activity in cultured amniotic cells, thus leading to therapeutic abortion. alpha-Mannosidase in the amniotic fluid of the fetuses with I-cell disease exhibited significant alterations in pH profile Km value, thermal stability and isoelectric focusing pattern, compared with the enzyme in normal controls. The results indicate that prenatal diagnosis of I-cell disease may be accomplished by demonstration of altered enzymological characteristics of alpha-mannosidase in the supernatant of amniotic fluid. The significance of the alteration of alpha-mannosidase in the amniotic fluid is not known.

ENZYMOLOGICAL DIAGNOSIS OF A GROUP OF LYSOSOMAL STORAGE DISEASES: REVIEW OF 5‐YEAR EXPERIENCE OF 1600 PATIENT‐SAMPLE REFERRALS

Lysosomal acid hydrolase activities have been measured in extracts of peripheral blood leucocytes of approximately 1600 patients referred from throughout Australia, each of whom was suspected of having a neurolipidosis. Assays for 12 different lysosomal enzymes were performed on each patient as a routine; ten assay systems were based on commercially available substrates, and four used radiolabelled glycosphingolipids prepared in our own laboratory. Of the 85 patients with positive results, 81 were diagnosed as being homozygous-deficient for a particular lysosomal enzyme. These patients comprised nine with GM1-gangliosidosis, 12 with GM2-gangliosidosis (11 of Tay-Sachs' disease and one of Sandhoff's disease), 18 with trihexosylceramide lipidosis (Fabry's disease), eight with beta-galactosylceramide lipidosis (Krabbe's disease), 14 with beta-glucosylceramide lipidosis (Gaucher's disease), two with sphingomyelin lipidosis (Niemann-Pick disease), 13 with metachromatic leucodystrophy and five with alpha-mannosidosis. In addition, four patients were diagnosed as being affected with mucolipidosis Type II (I-cell disease), based on elevated plasma lysosomal enzyme activities, making a total of 85 homozygous-affected patients. Clinically the patients showed wide phenotypic variability within each of the enzyme-deficient states, which did not appear to correlate with the level of "residual" enzyme activity in their leucocyte extracts.

Experimental arthritis produced by proteoglycan antigens in rabbits.

Spontaneous synovitis developed in the limb joints and rheumatoid factor-like component appeared in the sera of two rabbits from a pool 36 animals in the course of a long-term immunization with bovine nasal cartilage antigens. A single intra-articular injection of proteoglycan antigens regularly provoked a heavy synovitis and cartilage destruction irrespective of whether the booster injections were administered in physiological saline, or in Freund's complete adjuvant. The dose-dependent severity of arthritis suggested that the antibody titre against proteoglycan antigens played an important role in this mechanism. The synovial extract and synovial fluid of knee joints injected with proteoglycan antigens showed an increased enzyme activity concerning the four acid hydrolases (acid phosphatase, cathepsin D, hyaluronidase and beta-glucuronidase). The high activity of lysosomal acid hydrolases which persisted for several months can derange the molecular structure of proteoglycans of cartilage. The degraded proteoglycans may trigger autoimmune reactions, and the process eventually leads to chronic inflammation and joint destruction.

Lysosomal acid hydrolase activities in the aging heart

Total activities of four lysosomal acid hydrolases in the hearts of aging mice have been studied. Hydrolase activities were assayed in whole hearts of male C57B1/6J mice at 2.5, 5, 11, 17, 21 and 27 months of age and were expressed as μmoles substrate hydrolyzed/h/mg protein. β-glucuronidase and arylsulfatase (A & B) activities increased linearly with age. Maximum activities of β-glucuronidase and arylsulfatase were observed at 27 months of age and were 35 and 38% higher respectively compared to activities at 2.5 months. N-acetyl- β-D-glucosaminidase activities changed with age in quadratic fashion. Activities at 2.5 months of age declined 20% by 5 months and then increased by 45% to a maximum by 27 months. Acid phosphatase activities did not change significantly through the age span studied. These results are correlated with electron microscopic observations on the accumulation of lipofuscin pigment granules with age in the myocardium. These observations suggest that the increased activities of certain lysosomal hydrolases during the life span and the accumulation of lipofuscin are positively correlated and that they may play an important role in the aging heart.

Effect of bioflavonoids on lysosomal acid hydrolases and lysosomal stability in adjuvant-induced arthritis.

In rats with adjuvant-induced arthritis, the effect of (+)-catechin (CA) and 0-(beta-hydroxyethyl) rutosides (HR) on the activity of certain lysosomal acid hydrolases, viz., beta-glucuronidase, beta-N-acetyl glucosaminidase and cathepsin D in serum, liver, kidney and spleen and the stability of liver lysosomes was studied. The activity of these enzymes in arthritic tissues and serum increased significantly. The total activity of beta-glucuronidase in the lysosome-rich fraction from arthritic liver was appreciably decreased, while its release was significantly increased. These results demonstrate the fragility of lysosomes in arthritic tissues. Administration of CA or HR to the arthritic animals was found to have a prophylactic action by stabilizing liver lysosomes and reducing the free lysosomal enzyme activities in serum, liver, kidney and spleen. CA was more effective than HR.