Cystyl aminopeptidase activity in the plasma, viscera and brain of the snake Bothrops jararaca

The relationship between plasma osmolality and cystyl aminopeptidase was characterized in the snake Bothrops jararaca and comparisons were made with the emerging picture of this relationship in rats. The profile of cystyl aminopeptidase activity under basal conditions was determined in the soluble and membrane-bound forms in visceral organs and in the central nervous system in comparison with that of alanyl aminopeptidase. The regional localization of cystyl and alanyl aminopeptidase activities was studied in the central nervous system. The basal level of plasma cystyl aminopeptidase, four- to six-fold higher than in rats, suggests its importance to help regulate circulating levels of neurohypophysial peptides in B. jararaca snake. The osmotic sensitivity of this plasma enzyme, undetectable in male, but about three-fold higher in female snakes than in rats, reveals a sexual dimorphism. In marked contrast to those observed in rats, low levels of soluble and particulate forms in the kidney indicate that cystyl aminopeptidase plays a minor metabolizing role at this anatomical location in B. jararaca. Despite of the regional-specific divergence between the levels of rat and snake enzymes, the bilaterally symmetric pattern of the diencephalic distribution of alanyl aminopeptidase reflects functional homologies between these two distantly related species.     

Peptidase activities in the semen from the ductus deferens and uterus of the neotropical rattlesnake Crotalus durissus terrificus

To understand the role of peptidases in seminal physiology of Crotalus durissus terrificus, intra- and inter-seasonal activity levels of acid (APA), basic (APB), puromycin-sensitive (APN-PS) and puromycin-insensitive neutral (APN-PI), cystyl (CAP), dipeptidyl-IV (DPPIV), type-1 pyroglutamyl (PAP-I) and prolyl-imino (PIP) aminopeptidases as well as prolyl endopeptidase (POP) were evaluated in soluble (SF) and/or membrane-bound (MF) fractions of semen collected from the ductus deferens of the male reproductive tract and from the posterior portion of the uterus. Seminal APB, PIP and POP were detected in SF, while other peptidases were detected in SF and MF. Only the convoluted posterior uterus in winter and autumn had semen. Relative to other examined peptidases, in general, APN-PI, APN-PS and APB activities were predominant in the semen from the uterus and throughout the year in the semen from the ductus deferens, suggesting their great relevance in the seminal physiology of C. d. terrificus. The levels of peptidase activities in the ductus deferens semen varied seasonally and were different from those of semen in the uterus, suggesting that their modulatory actions on susceptible peptides are integrated to the male reproductive cycle events and spermatozoa viability of this snake.     

Effects of changes in hydromineral balance on rat brain aspartyl, arginyl, and alanyl aminopeptidase activities.

In order to examine the possible relationship between the processing and inactivation roles of aminopeptidases and the disruption of water-electrolyte balance, we measured the activities of aspartyl aminopeptidase (Asp-Ap), arginyl aminopeptidase (Arg-Ap) and alanyl aminopeptidase (Ala-Ap) in certain brain areas (hypothalamus, hippocampus, thalamus and brain cortices) and in the pituitary gland in several models of hydrosaline change. The activity of hypothalamic membrane-bound Asp-Ap significantly decreased (more than 50%) following treatments which induced a hypovolemic state. Aminopeptidase M activity (membrane-bound Ala-Ap activity with low sensitivity to puromycin) was also significantly decreased by 53 % in the thalamus of rats under conditions of hypovolemia plus hyperosmolality in comparison to the control group. These results indicate that aminopeptidases in the central nervous system may be involved in the physiological regulation of hydromineral balance.     

Digestive proteolysis in the Colorado potato beetle,Leptinotarsa decemlineata: Activity-based profiling and imaging of a multipeptidase network

The Colorado potato beetle (CPB), Leptinotarsa decemlineata, is a major pest of potato plants, and its digestive system is a promising target for development of pest control strategies. This work focuses on functional proteomic analysis of the digestive proteolytic enzymes expressed in the CPB gut. We identified a set of peptidases using imaging with specific activity-based probes and activity profiling with selective substrates and inhibitors. The secreted luminal peptidases were classified as: (i) endopeptidases of cathepsin D, cathepsin L, and trypsin types and (ii) exopeptidases with aminopeptidase (cathepsin H), carboxypeptidase (serine carboxypeptidase, prolyl carboxypeptidase), and carboxydipeptidase (cathepsin B) activities. The proteolytic arsenal also includes non-luminal peptidases with prolyl oligopeptidase and metalloaminopeptidase activities. Our results indicate that the CPB gut employs a multienzyme network of peptidases with complementary specificities to efficiently degrade ingested proteins. This proteolytic system functions in both CPB larvae and adults and is controlled mainly by cysteine and aspartic peptidases and supported by serine and metallopeptidases. The component enzymes identified here are potential targets for inhibitors with tailored specificities that could be engineered into potato plants to confer resistance to CPB.     

Effects of alpha1-adrenergic receptor blockade by doxazosin on renin-angiotensin system-regulating aminopeptidase and vasopressin-degrading activities in male and female rat thalamus.

The thalamus has connections with central autonomic centers involved in cardiovascular control and is enervated by noradrenergic fibers. The excitability of thalamic neurons is due to a reduction of ionic currents mediated by alpha(1)-adrenoceptors. The brain renin- angiotensin system (RAS) and the peptide hormone arginine-vasopressin (AVP) are also involved in the central control of blood pressure, and fluid and electrolyte homeostasis. It has been extensively reported that aminopeptidase A (APA), aminopeptidase B (APB), aminopeptidase N (APN), and vasopressin-degrading cystyl aminopeptidase activity (AVP-DA) play an important role in the regulation of the activity of angiotensins and AVP. We have analyzed the effect of alpha(1)-adrenoceptor blockade by doxazosin on RAS-regulating aminopeptidase activities and AVP-DA in soluble and membrane-bound fractions of male and female rat thalamus. Our results show that alpha(1)-adrenoceptors blockade by doxazosin does not modify the RAS through its degrading peptidases at thalamic level either in male or female rats. However, alpha(1)-adrenoceptors blockade shows gender differences in AVP-DA, increasing in males but not in females, supporting an increased capacity of males against females to degrade AVP and, therefore, to regulate cardiovascular homeostasis, under this pharmacological manipulation.     

Pentylenetetrazol-induced seizures affect the levels of prolyl oligopeptidase, thimet oligopeptidase and glial proteins in rat brain regions, and attenuation by MK-801 pretreatment

The regulatory mechanisms of neuropeptide-metabolizing enzymes often play a critical role in the pathogenesis of neuronal damage. A systemic administration of pentylenetetrazol (PTZ), an antagonist of GABA(A) receptor ion channel binding site, causes generalized epilepsy in an animal model. In the present study, we examined the involvement of prolyl oligopeptidase (POP), thimet oligopeptidase/neurolysin (EP 24.15/16) and glial proteins in PTZ-treated rat brain regions, and the suppressive effect of MK-801, a non-competitive NMDA receptor antagonist, pretreatment for their proteins. The activity of POP significantly decreased in the hippocampus at 30min and 3h, and in the frontal cortex at 3h after PTZ treatment, and pretreatment with MK-801 recovered the activity in the cortex at 3h. The activity of EP 24.15/16 significantly decreased in the hippocampus at 3h and 1 day, and in the cortex at 3h after the PTZ administration, whereas pretreatment with MK-801 recovered the change of the activity. The Western blot analysis of EP 24.15 showed significant decrease of the protein level in the hippocampus 3h after the PTZ treatment, whereas pretreatment with MK-801 recovered. The expression of GFAP and CD11b immunohistochemically increased in the hippocampus of the PTZ-treated rat as compared with controls. Pretreatment with MK-801 also recovered the GFAP and CD11b expression. These data suggest that PTZ-induced seizures of the rats cause indirect activation of glutamate NMDA receptors, then decrease POP and EP 24.15/16 enzyme activities and EP 24.15 immunoreactivity in the neuronal cells of the hippocampal formation. We speculate that changes of those peptidases in the brain may be related to the levels of the neuropeptides regulating PTZ-induced seizures.     

Effect of neonatal handling on brain enkephalin-degrading peptidase activities.

Neonatal handling decreases neutral endopeptidase 24.11 activity in the amygdala. However, this procedure does not affect aminopeptidase activities in any of the brain areas studied. Neonatal handling has been one of the most commonly used strategies to study the plasticity of the nervous system. The crucial role of the opioids in the control of different aspects of behaviour and development has been well documented. Regarding this subject, the endogenous opioid system might mediate some of the effects induced by neonatal handling. In this work, we have studied the effects of neonatal handling on several enkephalin-degrading peptidases, including soluble and membrane-bound aminopeptidases (puromycin-sensitive and -insensitive) and neutral endopeptidase 24.11 in different rat brain areas. Tyrosine aminopeptidase activities were measured fluorimetrically using tyrosine-beta-naphthylamide as substrate and puromycin as selective inhibitor of one of the membrane-enzymes. Dansyl-D-Ala-Gly-Phe(pNO2)-Gly was the fluorogenic substrate for neutral endopeptidase. The reduced neutral endopeptidase 24.11 activity in the amygdala of neonatal handled rats could reduce enkephalin catabolism in this area and it could be responsible for some of the effects induced by neonatal handling.     

Effects of morphine administration and its withdrawal on rat brain aminopeptidase activities

The endogenous opioid neuropeptide system seems to be involved in the neural processes which underlie drug addiction. Several studies have reported that the administration of morphine induces changes in the levels and/or activity of endogenous opioid peptides (enkephalin, dynorphin) and their precursors in specific brain regions of the adult CNS. The aim of this work was to study the effects of chronic morphine exposure and its withdrawal on certain aminopeptidases capable of degrading opioid peptides in brain areas including the amygdala, hypothalamus, hippocampus, striatum and brain cortices. In animals treated with morphine, aminopeptidase N presented higher enzyme activity levels in the striatum, the hypothalamus and the amygdala compared to control animals, although statistically significant differences were observed only in the case of the striatum. In addition, the activity of soluble puromycin-sensitive aminopeptidase (PSA) was found to be higher in the frontal cortex of these rats. In contrast, rats experiencing withdrawal symptoms presented decreased levels of aminopeptidase activity in certain brain areas. Thus, the activity of aminopeptidase N in the hippocampus and soluble puromycin-sensitive aminopeptidase in the frontal cortex were found to be lower in rats experiencing naloxone precipitated withdrawal symptoms, compared to the corresponding controls. Finally, the activity of the three studied aminopeptidases in vitro was unaltered by incubation with morphine, suggesting that the observed effects are not due to a direct action of this opioid upon the aminopeptidases. The results of the present report indicate that aminopeptidases may play an important role in the processes of tolerance and withdrawal associated with morphine administration.     

Effects of orchidectomy and testosterone replacement on mouse pyrrolidone carboxypeptidase activity in the HPA axis.

Pyrrolidone carboxypeptidase, also known as pyroglutamyl aminopeptidase, removes pyroglutamyl terminal residues from biologically active peptides such as thyrotropin-releasing hormone. The aim of the present work was to study the influence of orchidectomy and testosterone replacement on soluble (pyrrolidone carboxypeptidase type I) and membrane-bound (pyrrolidone carboxypeptidase type II) activities in the hypothalamus-pituitary-adrenal axis. Forty male mice (Balb/C) were distributed into five groups: sham-operated controls, orchidectomized, and orchidectomized treated with increasing doses of testosterone in each group (3, 6 and 12 mg/kg). In the hypothalamus, orchidectomy increased pyrrolidone carboxypeptidase type I, whereas the highest dose of testosterone returned this activity to control levels. In the pituitary, neither pyrrolidone carboxypeptidase type I nor type II activities changed after orchidectomy, although both activities increased after administration of testosterone in both cases. On the other hand, orchidectomy increased pyrrolidone carboxypeptidase type I and type II activities in adrenal glands, while testosterone replacement returned it to control levels. These results suggest that testosterone differentially modulates pyrrolidone carboxypeptidase type I and type II activities, and therefore also their endogenous substrate regulation. Thus, the influence of sex hormones in the physiology of the HPA axis through the modulation of the Pyrrolidone carboxypeptidase type I and type II activities is of great importance on stress and neuropathology associated with HPA dysfunction     

Novel prolyl tri/tetra-peptidyl aminopeptidase from Streptomyces mobaraensis: substrate specificity and enzyme gene cloning

The prolyl peptidase that removes the tetra-peptide of pro-transglutaminase was purified from Streptomyces mobaraensis mycelia. The substrate specificity of the enzyme using synthetic peptide substrates showed proline-specific activity with not only tripeptidyl peptidase activity, but also tetrapeptidyl peptidase activity. However, the enzyme had no other exo- and endo-activities. This substrate specificity is different from proline specific peptidases so far reported. The enzyme gene was cloned, based on the direct N-terminal amino acid sequence of the purified enzyme, and the entire nucleotide sequence of the coding region was determined. The deduced amino acid sequence revealed an N-terminal signal peptide sequence (33 amino acids) followed by the mature protein comprising 444 amino acid residues. This enzyme shows no remarkable homology with enzymes belonging to the prolyl oligopeptidase family, but has about 65% identity with three tripeptidyl peptidases from Streptomyces lividans, Streptomyces coelicolor, and Streptomyces avermitilis. Based on its substrate specificity, a new name, "prolyl tri/tetra-peptidyl aminopeptidase," is proposed for the enzyme.     

The efficiency of human cytomegalovirus pp65(495-503) CD8+ T cell epitope generation is determined by the balanced activities of cytosolic and endoplasmic reticulum-resident peptidases

Control of human CMV (HCMV) infection depends on the cytotoxic activity of CD8(+) CTLs. The HCMV phosphoprotein (pp)65 is a major CTL target Ag and pp65(495-503) is an immunodominant CTL epitope in infected HLA-A*0201 individuals. As immunodominance is strongly determined by the surface abundance of the specific epitope, we asked for the components of the cellular Ag processing machinery determining the efficacy of pp65(495-503) generation, in particular, for the proteasome, cytosolic peptidases, and endoplasmic reticulum (ER)-resident peptidases. In vitro Ag processing experiments revealed that standard proteasomes and immunoproteasomes generate the minimal 9-mer peptide epitope as well as N-terminal elongated epitope precursors of different lengths. These peptides are largely degraded by the cytosolic peptidases leucine aminopeptidase and tripeptidyl peptidase II, as evidenced by increased pp65(495-503) epitope presentation after leucine aminopeptidase and tripeptidyl peptidase II knockdown. Additionally, with prolyl oligopeptidase and aminopeptidase B we identified two new Ag processing machinery components, which by destroying the pp65(495-503) epitope limit the availability of the specific peptide pool. In contrast to cytosolic peptidases, silencing of ER aminopeptidases 1 and 2 strongly impaired pp65(495-503)-specific T cell activation, indicating the importance of ER aminopeptidases in pp65(495-503) generation. Thus, cytosolic peptidases primarily interfere with the generation of the pp65(495-503) epitope, whereas ER-resident aminopeptidases enhance such generation. As a consequence, our experiments reveal that the combination of cytosolic and ER-resident peptidase activities strongly shape the pool of specific antigenic peptides and thus modulate MHC class I epitope presentation efficiency.     

Altered expression of NCAM in hippocampus and cortex may underlie memory and learning deficits in rats with streptozotocin-induced diabetes mellitus

Neurological and structural changes are paralleled by cognitive deficits in diabetes mellitus. The present study was designed to evaluate the expression of neural cell adhesion molecules (NCAM) in the hippocampus, cortex and cerebellum and to examine cognitive functions in diabetic rats. Diabetes was induced in male albino rats via intraperitoneal streptozotocin injection. Learning and memory behaviors were investigated using a passive avoidance test and a spatial version of the Morris water maze test. NCAM expression was detected in the hippocampus, cortex and cerebellum by an immunoblotting method. The diabetic rats developed significant impairment in learning and memory behaviours as indicated by deficits in passive avoidance and water maze tests as compared to control rats. Expression of NCAM 180 and 120 kDa were found to be higher in hippocampus and cortex of diabetic rat brains compared to those of control, whereas expression of NCAM 140 kDa decreased in these brain regions. Our findings suggest that streptozotocin-induced diabetes impairs cognitive functions and causes an imbalance in expression of NCAM in those brain regions involved in learning and memory. Altered expression of NCAM in hippocampus may be an important cause of learning and memory deficits that occur in diabetes mellitus.     

Localization of angiotensin-converting enzyme,prolyl endopeptidase and other peptidases in cultured neuronal or glial cells

To determine the cellular localization of nervous tissue peptidases, 7 peptidases and 2 lysosomal marker enzyme activities were measured in cultured mouse and rat cells. Neuronal cells of both species exhibited higher activities of angiotensin-converting enzyme (ACE) and prolyl endopeptidase (Pro-EP) than glial cells did. In contrast, arginyl endopeptidase and lysosomal enzymes (acid phosphatase, β-glucuronidase) in the neuronal cell lines were lower than those in the glial cell lines. Other peptidases (alanyl aminopeptidase, arginyl aminopeptidase, leucyl aminopeptidase, dipeptidyl aminopeptidase) activities were not specifically localized in either cell lines. The effects of cellular differentiation on these peptidase activities in the PC 12h cell line and rat glioblasts were also examined using nerve growth factor (NGF) and glia maturation factor (GMF), respectively. Neuron specific peptidase (ACE and Pro-EP) activities were decreased in PC12h cells cultured with NGF, and Pro-EP activity was increased in the glioblast cells cultured with GMF. These results support the idea that some of the peptidases are differentially localized in neuronal or glial cells, and play physiological roles in central or peripheral neural tissues.     

Peptidases play an important role in cataractogenesis: an immunohistochemical study on lenses derived from Shumiya cataract rats

The role of proteolytic enzymes in Shumiya cataract rats in alterations to lens proteins during cataract formation was studied immunohistochemically using antibodies against exopeptidases, such as lysosomal dipeptidyl peptidase II (DPP II), cytosolic dipeptidyl peptidase III, and soluble and membrane-bound alanyl aminopeptidases, and against cytosolic endopeptidases such as mu- and m-calpains, and 20S proteasome. AlphaB-crystallin was detected as a proteolytic marker in the lenses. A constant immunoreactivity against all the antibodies employed was observed in the lens epithelium independent of the strain and age of the rats. A weak immunoreactivity against exo- and endopeptidases and an intense reactivity against alphaB-crystallin were observed in the lens fibres of control rats at all ages. The immunoreactivity of these peptidases in lens fibres increased with age in cataract rats, but that of alphaB-crystallin decreased. No reactivity against exo- and endopeptidases was seen in the perinuclear region of lenses of control rats at all ages or in Shumiya cataract rats at 8 and 10 weeks of age, but an intense reactivity against these peptidases was observed in the lens perinuclear region of lenses in cataract rats at 12 and 14 weeks of age. AlphaB-crystallin immunoreactivity was observed with ordered striations in the lens perinuclear region of all control rats whereas the striations in this area of cataract rat lens were disorganized. Membrane-bound alanyl aminopeptidase was detected feebly in the lens epithelium and fibres of both types of rat at all weeks of age. These findings indicate that exo- and endopeptidases, except for membrane-bound alanyl aminopeptidase, are expressed intensively and are age-dependent. Conversely, the amount of alphaB-crystallin decreased with age in lens fibres of cataract rats. Calpains (mu- and m-), 20S proteasome, dipeptidyl peptidases II and III and soluble alanyl aminopeptidase are thought to induce lens opacification kinetically during cataract formation in Shumiya cataract rats through the intracellular turnover of lens proteins.     

Structural relationship between lipases and peptidases of the prolyl oligopeptidase family.

In prolyl oligopeptidase and its homologues, which constitute a new serine protease family, the order of the catalytic Ser and His residues in the amino acid sequence is the reverse of what is found in the trypsin and subtilisin families. The exact position of the third member of the catalytic triad, an Asp residue, has not yet been identified in the new family. Recent determination of the three-dimensional structures of pancreatic and microbial lipases has shown that the order of their catalytic residues is Ser, Asp, His, and this fits the order Ser, His of prolyl oligopeptidase. However, there is no sequence homology between lipases and peptidases, except for a 10-residue segment, which encompasses the essential Ser, and for the immediate vicinity of the catalytic Asp and His residues. This comparison identifies the catalytic Asp residue in the prolyl oligopeptidase family. The relative positions of the three catalytic residues in peptidases and microbial lipases were the same and this indicated structural and possibly evolutionary relationship between the two families.     

Specific inhibition of endopeptidase 24.16 by dipeptides.

The inhibitory effect of various dipeptides on the neurotensin-degrading metallopeptidase, endopeptidase 24.16, was examined. These dipeptides mimick the Pro10-Tyr11 bond of neurotensin that is hydrolyzed by endopeptidase 24.16. Among a series of Pro-Xaa dipeptides, the most potent inhibitory effect was elicited by Pro-Ile (Ki approximately 90 microM) with Pro-Ile greater than Pro-Met greater than Pro-Phe. All the Xaa-Tyr dipeptides were unable to inhibit endopeptidase 24.16. The effect of Pro-Ile on several purified peptidases was assessed by means of fluorigenic assays and HPLC analysis. A 5 mM concentration of Pro-Ile does not inhibit endopeptidase 24.11, endopeptidase 24.15, angiotensin-converting enzyme, proline endopeptidase, trypsin, leucine aminopeptidase, pyroglutamyl aminopeptidase I and carboxypeptidase B. The only enzyme that was affected by Pro-Ile was carboxypeptidase A, although it was with a 50-fold lower potency (Ki approximately 5 mM) than for endopeptidase 24.16. By means of fluorimetric substrates with a series of hydrolysing activities, we demonstrate that Pro-Ile can be used as a specific inhibitor of endopeptidase 24.16, even in a complex mixture of peptidase activities such as found in whole rat brain homogenate.     

Thyrotrophin-releasing hormone inactivation by human postmortem brain

The mechanisms of inactivation of thyrotrophin-releasing hormone (TRH) by peptidases in several areas of normal human postmortem brain have been investigated by radioimmunoassay and high-performance liquid chromatography. Of the several brain regions studied, the cerebral cortex (Brodman's area, BA10) had the highest TRH-degrading activity in both subcellular fractions. Deamidated-TRH (TRH-OH) was the only product formed by the soluble fraction whereas the histidyl-proline diketopiperazine, cyclo(His-Pro), and a small amount of TRH-OH were formed by the particulate fraction. Several centrally acting TRH analogues showed varying degrees of resistance to degradation by the peptidases in the two fractions, the most stable analogue being RX77368 (pGlu-His-3,3'-dimethyl(ProNH2]. Areas of human postmortem brain appear to contain two of the enzymes capable of degrading TRH, a proline endopeptidase forming TRH-OH and a pyroglutamyl aminopeptidase forming cyclo(His-Pro). The use of the assay procedures in further studies on the inactivation of TRH by peptidases from brain areas of patients with neurological disorders may provide complementary information on the dynamics of TRH in these disorders. The stability of the centrally acting TRH analogues may prove useful in examining their therapeutic potential.     

An Essential Signal Peptide Peptidase Identified in an RNAi Screen of Serine Peptidases of Trypanosoma brucei

The serine peptidases of Trypanosoma brucei have been viewed as potential drug targets. In particular, the S9 prolyl oligopeptidase subfamily is thought to be a good avenue for drug discovery. This is based on the finding that some S9 peptidases are secreted and active in the mammalian bloodstream, and that they are a class of enzyme against which drugs have successfully been developed. We collated a list of all serine peptidases in T. brucei, identifying 20 serine peptidase genes, of which nine are S9 peptidases. We screened all 20 serine peptidases by RNAi to determine which, if any, are essential for bloodstream form T. brucei survival. All S9 serine peptidases were dispensable for parasite survival in vitro, even when pairs of similar genes, coding for oligopeptidase B or prolyl oligopeptidase, were targeted simultaneously. We also found no effect on parasite survival in an animal host when the S9 peptidases oligopeptidase B, prolyl oligopeptidase or dipeptidyl peptidase 8 were targeted. The only serine peptidase to emerge from the RNAi screen as essential was a putative type-I signal peptide peptidase (SPP1). This gene was essential for parasite survival both in vitro and in vivo. The growth defect conferred by RNAi depletion of SPP1 was rescued by expression of a functional peptidase from an RNAi resistant SPP1 gene. However, expression of catalytically inactive SPP1 was unable to rescue cells from the SPP1 depleted phenotype, demonstrating that SPP1 serine peptidase activity is necessary for T. brucei survival.     

Effect of Long-Lasting Diabetes Mellitus on Rat and Human Brain Monoamines

Experimental alloxan- or streptozotocin-produced diabetes in rats was accompanied by an increase in the levels of norepinephrine, dopamine, and serotonin, whereas the contents of metabolites, i.e., 5-hydroxyindoleacetic acid and homovanillic acid, in the whole brain gradually decreased with the duration of diabetes. Among the striatum, thalamus, and hypothalamus of alloxan diabetic rats, monoamine alterations were observed only in the hypothalamus; after 1 week an increase of norepinephrine content and after 13 weeks an increase of norepinephrine and dopamine contents were found. Tissues of 11 brain regions of 10 diabetic and 12 control patients post mortem were investigated for monoamine concentrations. Patients were all male, of similar age and interval between death and autopsy. Diabetic patients had an increase in the content of serotonin in the medial and lateral hypothalamus. The content of dopamine increased in the medial hypothalamus, putamen, and medial and lateral pallidus. In diabetic patients, the content of norepinephrine increased in the lateral pallidus and decreased in the nucleus accumbens and claustrum. Thus, it seems that diabetes mellitus in rats, as well as in humans is associated with regionally specific changes in brain monoamines.     

Comparative distribution of glutamyl and aspartyl aminopeptidase activities in mouse organs.

To evaluate the functional role of glutamyl and aspartyl aminopeptidases, their soluble and membrane-bound activities were measured simultaneously in several tissues of normal mice using arylamide derivatives as substrates. Although the soluble aspartyl aminopeptidase activity showed its highest levels in the testicle, the rest of the activities presented their highest levels in the kidney. Different patterns of distribution were observed for glutamyl and aspartyl aminopeptidase activities and also for soluble and membrane-bound aspartyl aminopeptidase activities. However no major differences were observed between soluble and membrane-bound glutamyl aminopeptidase activities. This unequal distribution suggests that the use of arylamide derivatives as substrates is a sensitive method that distinguishes between these enzymatic activities. The results also suggest different functions for soluble and membrane-bound aspartyl aminopeptidase activities, and for glutamyl and aspartyl aminopeptidase activities.