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PubMed2006

Mitochondrial membrane potential and reactive oxygen species content of endothelial and smooth muscle cells cultured on poly(epsilon-caprolactone) films.

A transitory but significant stimulation of mitochondrial activity, increase of reactive oxygen species (ROS) and oxidative stress were previously observed in L929 fibroblasts cultured on poly(epsilon-caprolactone) (PCL) films. ROS, mainly formed in mitochondria, play a physiological role but an excessive production can promote endothelial dysfunction, cause oxidative injury to vascular cells, oxidize lipoproteins and accelerate atherothrombogenesis. On the other hand, mitochondria have a crucial position in programmed cell death control and are responsible for ATP synthesis through the coupling of oxidative phosphorylation to respiration. This coupling requires the existence of a mitochondrial membrane potential (Deltapsi(m)). The aim of the present study was to evaluate by flow cytometry the ROS content and Deltapsi(m) of both endothelial (EC) and smooth muscle cells (SMC) cultured on PCL films as a potential substrate for vascular graft development. Cell size, internal complexity and cell cycle were also analyzed to detect the possible appearance of the subG(1) cell fraction, characteristic of apoptotic cells. The effect of treating PCL films with NaOH before culture was also studied. PCL decreases the ROS content of EC during the culture but produces an increase of these levels in SMC after 7 days. PCL also induces variations of Deltapsi(m) which show a significant parallelism with the changes observed in ROS levels proving the importance and sensitivity of these measurements as indicators of the mitochondrial function. The treatment of PCL with NaOH decreases these effects demonstrating the benefits of increasing the surface hydrophilicity before cell culture which improves cell adhesion and proliferation and reduces oxidative stress. Since no important changes have been detected in subG(1) fraction of EC and SMC cultured on either PCL or PCL-NaOH, the changes of Deltapsi(m) observed in the present study cannot be related to apoptosis. These results confirm the potential utility of PCL as a suitable scaffold in Vascular Tissue Engineering.

Animals↗

PubMed2002

Insights into steroidogenic acute regulatory protein (StAR)-dependent cholesterol transfer in mitochondria: evidence from molecular modeling and structure-based thermodynamics supporting the existence of partially unfolded states of StAR.

The steroidogenic acute regulatory protein (StAR) is the major entrance for cholesterol in mitochondria under acute stimulation. Under such circumstances, dysfunctional StAR activity can ultimately lead to lipoid congenital adrenal hyperplasia (LCAH). A complete understanding of the StAR's molecular structure and mechanism is essential to comprehend LCAH. Thus far, there is no mechanistic model that can explain experimental results at the molecular level. This is partly due to the lack of the molecular structure of StAR. The closest approximation to the StAR molecular structure is the human MLN64 which has a similar activity to StAR, has a highly homologous primary structure and for which an X-ray structure is known. In this context, we have modeled the structure of StAR through standard homology modeling procedures based on the MLN64 structure. Our StAR model shows the presence of a hydrophobic cavity of 783.9 A(2) in surface area, large enough to fit one molecule of cholesterol. In addition, we have identified a unique charged pair, as in MLN64, lining the surface of the cavity and which could play a key role in the binding of cholesterol through the formation of an H-bond with its OH moiety. This suggests that the cholesterol-binding site of StAR is located inside this cavity. Taking into account that internal cavities are destabilizing to native protein structures and that the lining of the cavity has to become accessible in order to allow cholesterol binding, we have explored the possibility that StAR could exist in equilibrium with partially unfolded states. Using a structure-based thermodynamics approach, we show that partially folded states (with an unfolded C-terminal alpha-helix, and an open cavity) can be significantly populated at equilibrium and therefore allow cholesterol binding. These results are supported by recent experiments that show a loss of StAR helical character upon binding of an analog of cholesterol. Moreover, we show that the replacement of the residues involved in the charged-pair located in the binding site results in the loss of StAR activity, supporting a key role for these residues. Taken together, our results are applicable to StAR functioning both in the mitochondrial intermembrane space as well as outside the mitochondria.

Amino Acid Sequence↗

PubMed2001

Targeting large molecules to mitochondria.

Mitochondrial function is central to a range of cell processes and mitochondrial dysfunction contributes to a number of human diseases. Consequently there is growing interest in delivering large molecules such as nucleic acids, proteins, enzyme mimetics, drugs and probes to mitochondria within cells. The reasons for doing this are to understand how mitochondria function in the cell and to develop therapies for diseases involving mitochondrial damage. Here we review the methods that have been used to target large molecules to mitochondria and discuss some approaches under development.

Animals↗

PubMed2005

Mitochondrial function and mitochondria-induced apoptosis in an overstimulated rat ovarian cycle.

Female rats were treated with FSH (40 IU/kg) on the first and second diestrus days (D1 and D2) and with LH (40 IU/kg) on the proestrus (P) day to synchronize and maximize ovarian changes. Follicle area increased by 50% from D1 to P, and the estrus (E) phase showed multiple corpora lutea and massive apoptosis. Increased oxygen uptakes (42-102%) were determined in ovary slices and in isolated mitochondria in active state 3 along the proliferation phase (D1-D2-P) that returned to initial values in the E phase. Mitochondrial content and the electron transfer activities of complexes I and IV were also maximal in the P phase (20-79% higher than in D1). Production of NO by mitochondrial nitric oxide synthase (mtNOS), biochemically determined, and the mtNOS functional activity in regulating state 3 oxygen uptake were also maximal at P and 79-88% higher than at D1. The moderately increased rate of NO in the proliferative phase is associated with mitochondrial biogenesis, whereas the high rate of NO generation by mtNOS at phase P appears to trigger mitochondria-dependent apoptosis. The calculated fraction of ovary mitochondria in state 3 was at a minimal value at the P phase. Mitochondrial oxidative damage, with increased thiobarbituric acid-reactive substances and protein carbonyls, indicates progressive mitochondrial dysfunction between phases P and E. The roles of mitochondria as ATP provider, as a source of NO to signal for mitochondrial proliferation and mitochondria-dependent apoptosis, and as a source of O(2)(-) and H(2)O(2) appear well adapted to serve the proliferation-apoptosis sequence of the ovarian cycle.

Animals↗

PubMed2006

Mitochondrial dysfunction and oxidative stress in neurodegenerative diseases.

Many lines of evidence suggest that mitochondria have a central role in ageing-related neurodegenerative diseases. Mitochondria are critical regulators of cell death, a key feature of neurodegeneration. Mutations in mitochondrial DNA and oxidative stress both contribute to ageing, which is the greatest risk factor for neurodegenerative diseases. In all major examples of these diseases there is strong evidence that mitochondrial dysfunction occurs early and acts causally in disease pathogenesis. Moreover, an impressive number of disease-specific proteins interact with mitochondria. Thus, therapies targeting basic mitochondrial processes, such as energy metabolism or free-radical generation, or specific interactions of disease-related proteins with mitochondria, hold great promise.

Aging↗

PubMed2005

Oxidative and nitrosative stress in brain mitochondria of diabetic rats.

Diabetic encephalopathy, characterized by impaired cognitive functions and neurochemical and structural abnormalities, may involve direct neuronal damage caused by intracellular glucose. The study assesses the direct effect of chronic hyperglycemia on the function of brain mitochondria, the major site of reactive species production, in diabetic streptozotocin (STZ) rats. Oxidative stress plays a central role in diabetic tissue damage. Alongside enhanced reactive oxygen species (ROS) levels, both nitric oxide (NO) levels and mitochondrial nitric oxide synthase expression were found to be increased in mitochondria, whereas glutathione (GSH) peroxidase activity and manganese superoxide dismutase protein content were reduced. GSH was reduced and GSH disulfide (GSSG) was increased in STZ rats. Oxidative and nitrosative stress, by reducing the activity of complexes III, IV and V of the respiratory chain and decreasing ATP levels, might contribute to mitochondrial dysfunction. In summary, this study offers fresh evidence that, besides the vascular-dependent mechanisms of brain dysfunction, oxidative and nitrosative stress, by damaging brain mitochondria, may cause direct injury of neuronal cells.

Animals↗

PubMed2004

[Aging-related increase of sensitivity of the mitochondrial permeability transition pore to inductors in the rat heart].

An age-related increase in the sensitivity of the mitochondrial permeability transition pore (MPTP) to inductors of it's opening, Ca2+ ions and phenylarsineoxide (PAO) was studied in experiments in vitro on isolated heart mitochondria of adult and old rats. Two indices were measured spectrophotometrically (lambda = 520 nm) by a decrease in an optical density (OD), resulting from mitochondrial swelling and a release of mitochondrial unidentified substances (mitochondrial factor, MF) registered also spectrophotometrically in a range of waves lambda = 230-260 nm. Dose-dependent effect of Ca2+ (10(-7)-10(-4) mol/l) and PAO (10(-8)-10(-4) mol/l) on swelling of the mitochondria were observed in samples from both adult and old rats. Swelling of the mitochondria from the heart of old rats induced by application of the above inductors was more intensive than the respective effect in samples from adult rats. In samples from the heart of both adult and old rats Ca2+ ions within the tested concentration range (10(-7)-10(-4) mol/l) evoked the release of MF in a dose-dependent manner. Mitochondria from the heart of old rats were found to be capable of releasing some amounts of MF in the absence of the MPTP inductors PAO. When this inductor was applied in a 10(-9) to 10(-4) mol/l concentration range, isolated mitochondria from the heart of old rats released unidentified substances with the absorption peaks at two wavelength, lambda = 230 nm and lambda = 240-245 nm. The former peak was found to be Cyclosporin A-insensitive, while the latter peak could be practically completely inhibited by this antibiotic. The concentrations of tested solutions (10(-7) mol/l CaCl2 and 10(-9) mol/l PAO), at which the release of the factor from the mitochondria of the old rat heart was observed, were significantly lower than those in adult rats. Our experimental data show that mitochondria isolated from the heart tissue of old rats demonstrate significantly higher sensitivity to inductors of MPTP-opening, Ca(2+)-overload and PAO as compared to that typical of adult animals. A higher sensitivity of MPTP-opening in the heart of old rats was accompanied by a higher basal level of expression of mRNA of the bax gene, as compared to that found in adult animals. The expression of the bcl-2 gene showed no age group-related differences. It can be supposed that a proapoptotic agent, the Bax protein, is related to an increase in the sensitivity of the MPTP (in particular to that manifested in the processes of pore formation) in the course of aging. Antioxidants, melathonin and trolox, when applied in 10(-5) mol/l concentration, presented to a certain extent opening of the MPTP-induced by 10(-5) mol/l PAO in samples from adult and old rats. These findings can be used for correction of increased sensitivity of the MPTP to different inductors, which is typical of old rats. We conclude that physiological aging is accompanied by the mitochondrial dysfunction. The MF-released capability of the mitochondria from heart tissue of old rats observed both in the presence and absence of MPTP-opening inductors (probably related to a higher sensitivity of MPTP-opening) is one of the manifestation of such dysfunction.

Aging↗

PubMed1996

Localization and amount of myoglobin and myoglobin mRNA in ragged-red fiber of patients with mitochondrial encephalomyopathy.

The localization and amounts of myoglobin (Mb) and Mb mRNA in ragged-red fibers (RRF) in skeletal muscle of 6 patients with mitochondrial encephalomyopathy were examined immunohistochemically and by in situ hybridization. The amounts of Mb and Mb mRNA were expressed in terms of optical densities (ODs) of Mb immunostaining and Mb mRNA signals. In nonatrophic RRF, Mb was predominantly seen in the ragged-red region and Mb mRNA signals were increased throughout the sarcoplasm. The amounts of Mb and Mb mRNA in nonatrophic RRF were greater than those in nonatrophic non-RRF. In contrast, the localization and amount in atrophic RRF were similar to those in atrophic non-RRF. Thus, Mb synthesis in nonatrophic RRF may increase to compensate for mitochondrial dysfunction and to supply sufficient oxygen to mitochondria, but this compensatory function may be impaired in atrophic RRF.

Adult↗

PubMed1991

Experimental germanium myopathy.

The long-term administration of germanium dioxide (GeO2) to rats produced Ge myopathy characterized by the formation of ragged-red fibers. The earliest pathological changes in experimental Ge myopathy were a decrease in cytochrome c oxidase activity and accumulation of high electron-dense materials in mitochondria. These findings suggest that a mitochondrial dysfunction may be most important in the genesis of experimental Ge myopathy, which could be a useful animal model for the investigation of and therapeutic trials for human mitochondrial myopathies.

Animals↗

PubMed2005

Mitochondrial DNA 3243A>G mutation and increased expression of LARS2 gene in the brains of patients with bipolar disorder and schizophrenia.

BACKGROUND: Accumulating evidence suggests mitochondrial dysfunction in bipolar disorder. Analyses of mitochondria-related genes using DNA microarray showed significantly increased LARS2 (mitochondrial leucyl-tRNA synthetase) in the postmortem prefrontal cortices of patients with bipolar disorder provided by the Stanley Foundation Brain Collection. LARS2 is a nuclear gene encoding the enzyme catalyzing the aminoacylation of mitochondrial tRNA(Leu). A well-studied mitochondrial DNA point mutation, 3243A>G, in the region of tRNA(Leu (UUR)), related with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes), is known to decrease the efficiency of aminoacylation of tRNA(Leu (UUR)). METHODS: The steady state level of LARS2 was examined in the transmitochondrial cybrids carrying 3243A>G. We examined the 3243A>G mutation in these brains using the peptide nucleic acid-clamped polymerase chain reaction restriction fragment length polymorphism method. RESULTS: LARS2 was upregulated in the transmitochrondrial cybrids carrying 3243A>G. The 3243A>G was detected in the postmortem brains of two patients with bipolar disorder and one with schizophrenia. These patients also showed higher levels of the mutation in their livers and significantly higher gene expression of LARS2 compared with other subjects. CONCLUSIONS: These results suggest that upregulation of LARS2 is a hallmark of 324A>G mutation. The accumulation of 3243A>G mutation in the brain may have a pathophysiologic role in bipolar disorder and schizophrenia.

Adult↗

PubMed2003

Effect of manganese chloride exposure on liver and brain mitochondria function in rats.

Manganese (Mn) is an essential trace element found in many enzymes. As is the case for many essential trace elements, excessive Mn is toxic. Individuals suffering from manganese toxicity exhibit several symptoms, which are similar to those frequently observed in cases of Parkinson's disease. In this investigation, we studied the effect of manganese chloride (7.5, 15.0, and 30.0 mg/kg body weight) on mitochondrial function and attempted to ascertain the mechanism of manganese-induced mitochondrial dysfunction. The production of reactive oxygen species in mitochondria of rat liver and brain was assayed using 2',7'-dichlorofluorescin diacetate, and the activities of respiratory chain enzymes were examined spectrophotometrically. Monoamine oxidase (MAO) activity was assayed by measuring reduction of benzylamine. Manganese and calcium content in mitochondria were determined by atomic absorption spectrophotometry. These results indicate that manganese chloride (MnCl2) can decrease MAO activity and inhibit the respiratory chain. Manganese can accumulate in mitochondria and inhibit efflux of calcium. There is a significant inverse correlation between the amount of superoxide radicals and the specific activities of the mitochondria enzymes. Mitochondrial function was significantly affected in both males and females.

Animals↗

PubMed1999

Mitochondrial dysfunction in the pathogenesis of necrotic and apoptotic cell death.

Mitochondria are frequently the target of injury after stresses leading to necrotic and apoptotic cell death. Inhibition of oxidative phosphorylation progresses to uncoupling when opening of a high conductance permeability transition (PT) pore in the mitochondrial inner membrane abruptly increases the permeability of the mitochondrial inner membrane to solutes of molecular mass up to 1500 Da. Cyclosporin A (CsA) blocks this mitochondrial permeability transition (MPT) and prevents necrotic cell death from oxidative stress, Ca2+ ionophore toxicity, Reye-related drug toxicity, pH-dependent ischemia/reperfusion injury, and other models of cell injury. Confocal fluorescence microscopy directly visualizes onset of the MPT from the movement of green-fluorescing calcein into mitochondria and the simultaneous release from mitochondria of red-fluorescing tetramethylrhodamine methylester, a membrane potential-indicating fluorophore. In oxidative stress to hepatocytes induced by tert-butylhydroperoxide, NAD(P)H oxidation, increased mitochondrial Ca2+, and mitochondrial generation of reactive oxygen species precede and contribute to onset of the MPT. Confocal microscopy also shows directly that the MPT is a critical event in apoptosis of hepatocytes induced by tumor necrosis factor-alpha. Progression to necrotic and apoptotic cell killing depends, at least in part, on the effect the MPT has on cellular ATP levels. If ATP levels fall profoundly, necrotic killing ensues. If ATP levels are at least partially maintained, apoptosis follows the MPT. Cellular features of both apoptosis and necrosis frequently occur together after death signals and toxic stresses. A new term, necrapoptosis, describes such death processes that begin with a common stress or death signal, progress by shared pathways, but culminate in either cell lysis (necrosis) or programmed cellular resorption (apoptosis) depending on modifying factors such as ATP.

Animals↗

PubMed2002

Mitochondrial dysfunction in sepsis: evidence from bacteraemic baboons and endotoxaemic rabbits.

Mitochondria, that provide most of the ATP needed for cell work, and that play numerous specific functions in biosyntheses and degradations, as well as contributing to Ca2+ signaling, also play a key role in the pathway to cell death. Impairment of mitochondrial functions caused by mutations of mt-genome, and by acute processes, are responsible for numerous diseases. The involvement of impaired mitochondria in the pathogenesis of sepsis is discussed. By means of the skinned fiber technique and high resolution respirometry, we have detected significantly reduced rates of mitochondrial respiration in heart and skeletal muscle of endotoxaemic rabbits. Mitochondria from heart were more affected than those from skeletal muscle. Decreased respiration rates were accompanied by reduced activities of complex I + III of the respiratory chain. Endotoxin-caused impairment was also detectable at the level of the Langendorff perfused heart, where the coronary vascular resistance was significantly increased. For an investigation of the influence of bacteraemia on the mitochondrial respiratory chain, baboons were made septic by infusion of high and low amounts of E. coli. For complex I + III and II + III, a clear dose-dependent decrease was detectable and in animals which died in septic shock, a further decrease of enzyme activities in comparison to the controls were found. These results are discussed in the light of current knowledge on the role of mitochondria in cell pathology in respect to sepsis. In conclusion, we present evidence that mitochondrial function is disturbed during sepsis. Besides ischaemic and poison-induced disturbances of mitochondrial function, sepsis is a further example of an acute disease where impaired mitochondria have to be taken into account.

Animals↗

PubMed1987

Pharmacology of Reye syndrome.

Reye syndrome, a reversible metabolic encephalopathy and hepatopathy, offers a unique opportunity to investigate the pharmacologic mechanisms by which a toxic-metabolic insult to mitochondria is translated into neurochemical and neurologic dysfunction. Similarity of some clinical and metabolic abnormalities between certain inborn errors of organic acid, ammonia, and carbohydrate metabolism and Reye syndrome suggests a common pathophysiologic mechanism at some level. The primary metabolic aberration in Reye syndrome is unknown. Viral, drug, and toxic precipitants in a conductive host alter glial and neuronal function, possibly by direct toxic effects or by altered transmitter metabolism and signal transduction. These events translate into a rather stereotyped progression of the clinical syndrome. Increased ICP, which is a life-threatening epiphenomenon, is the focus of conventional therapy. Investigational treatments, still in preliminary stages, are aimed at early correction of instigating metabolic abnormalities or correction of their consequences on central neurotransmission. Our fragmentary knowledge of neurotransmitter abnormalities in this disorder, which have suggested disparate interpretations, does not allow a cohesive pharmacologic theory of Reye syndrome. The greatest difficulties in interpretation of possible central mechanisms from existing data, which derive largely from peripheral tissues, is in the differentiation of primary from compensatory changes. The unitarian notion that a single pharmacologic disturbance is the source of the encephalopathy is perhaps too simplistic. It is hoped that future studies of disorders such as Reye syndrome will elucidate the intricate relationships between biochemical pathways and neurotransmitter metabolism.

Amino Acids↗

PubMedDate not supplied

Oxidative stress and pancreatic beta-cell dysfunction.

Oxidative stress is induced under diabetic conditions through various pathways, including the electron transport chain in mitochondria and the nonenzymatic glycosylation reaction, and is likely involved in progression of pancreatic beta-cell dysfunction developing in diabetes. beta-Cells are vulnerable to oxidative stress, possibly due to low levels of antioxidant enzyme expression. When oxidative stress was induced in vitro in beta cells, the insulin gene promoter activity and mRNA levels were suppressed, accompanied by the reduced activity of pancreatic and duodenal homeobox factor-1 (PDX-1) (also known as IDX-1/STF-1/IPF1), an important transcription factor for the insulin gene. The suppression of oxidative stress by a potent antioxidant, N-acetyl-l-cysteine or probucol, led to the recovery of insulin biosynthesis and PDX-1 expression in nuclei and improved glucose tolerance in animal models for type 2 diabetes. As a possible cause of this, we recently found that PDX-1 was translocated from the nucleus to the cytoplasm in response to oxidative stress. Furthermore, the addition of a dominant-negative form of c-Jun N-terminal kinase (JNK) inhibited the oxidative stress-induced PDX-1 translocation, suggesting an essential role of JNK in mediating the phenomenon. Taken together, the oxidative stress-mediated activation of the JNK pathway leads to nucleocytoplasmic translocation of PDX-1 and thus is likely involved in the progression of beta-cell dysfunction found in diabetes.

Animals↗

PubMed1985

Significance of adenosinetriphosphate in human sperm as clinical parameter.

Washed human spermatozoa from 21 individuals with an average motility of 60% (quality index 277 +/- 16) had an endogenous ATP generation of 7.5 +/- 3.4 nmole/10(8) spermatozoa. The ATP concentrations in spermatozoa from 16 patients with severely impaired motility of 26% (quality index 98 +/- 13) was 16.9 +/- 9.9 nmole/10(8) spermatozoa. There was no correlation between ATP content and motility in either group. Sperm penetration into blood serum type AB, Rh-positive, was evaluated using a capillary tube penetration test. The penetration was graded with a maximum score of 14. Spermatozoa with an initial motility of 60% reached a score of 10 +/- 0.7. After addition of 20 mmole of ATP the score was significantly improved to 13 +/- 0.3. Compared with these results spermatozoa with an average motility of 26% reached a score of 4 +/- 1. Exogenous ATP (20 mmole) increased the score to 8 +/- 1.0. In both groups reduced glutathione had a negative effect. Human spermatozoa with high and low motility are capable to synthesize ATP. A dysfunction of the phosphorylating particles in the mitochondria appears not to be associated with low sperm motility.

ABO Blood-Group System↗

PubMed2001

Chorion laeve trophoblasts of preeclamptic fetal membranes: histochemically detectable enzyme activities do not change at a subcellular level.

We examined the subcellular localization of ADP-degrading activity and cytochrome c oxidase (CCO) activity in chorion laeve trophoblasts from term and near term human fetal membranes, and compared them with those from severe preeclamptic fetal membranes. The methods used for the detection of enzyme activities were the lead nitrate method for ADP-degrading activity and the diaminobenzidine method for CCO. Precipitates indicative of ADP-degrading activity were visible on surface microvillous plasma membranes of chorion laeve trophoblasts both from normal and preeclamptic fetal membranes. The intensity and distribution patterns were the same in the normal and preeclamptic subjects. CCO labeling was visible in almost all laeve trophoblastic mitochondria both in normal and preeclamptic cases. Previously, we demonstrated that in preeclamptic villous trophoblasts there were decreases in ADP-degrading activity and the presence of CCO-negative mitochondria, which were proposed to lead to dysfunction of each villous trophoblast, and finally to placental insufficiency in preeclampsia. Reductions or changes in enzyme intensities/distribution patterns, which are characteristic features of preeclamptic villous trophoblasts, were absent in chorion laeve trophoblasts in preeclampsia. These results suggest that in preeclampsia there are no, or at least less severe, abnormalities in the enzyme activities of chorion laeve trophoblasts, compared with villous trophoblasts, as far as enzyme-histochemically detectable enzymes are concerned.

Adult↗

PubMed1991

Low level developmental lead exposure decreases the sensitivity, amplitude and temporal resolution of rods.

Electroretinographic (ERG), morphometric and biochemical studies on retinas from monkeys or rats reveal that moderate level developmental lead (Pb) exposure produces long-term selective rod deficits and degeneration. The present studies determined whether similar alterations occur following low level developmental Pb exposure. Long-Evans rats, exposed to Pb only via dam's milk from parturition to weaning, had mean blood Pb of 18.8 micrograms/dl at weaning and 6.6 micrograms/dl at 90 days of age. Morphometric and ultrastructural studies revealed no signs of rod loss or degeneration although the presence of glycogen in some rod mitochondria suggests the occurrence of a metabolic dysfunction. Retinal sensitivity and rhodopsin content per eye were decreased in a manner such that, they followed the established log-linear relationship. A- and b-wave voltage- and latency-log intensity functions, generated from single-flash ERGs in fully dark-adapted rats, revealed that low level Pb exposure caused a 25% and 15% decrease in mean amplitude, a 0.5 and a 0.5 log unit decrease in absolute sensitivity, and a 23% and 16% increase in mean latency, respectively. Scotopic (rod-mediated) and photopic (cone-mediated) flicker fusion frequency measures revealed selective rod deficits. Adult rats had a 15% inhibition of retinal cGMP-phosphodiesterase resulting in a 19% and 12% increase in cGMP in dark- and light-adapted states, respectively. The above data confirm and extend our previous studies conducted in rats with blood lead levels of 59 micrograms/dl during development. The rhodopsin and cyclic nucleotide metabolism data, as well as our recent data showing an inhibition of retinal Na+, K(+)-ATPase, are entirely consistent with the observed ERG changes. The fact that rat rods are similar to monkey and human rods suggests the relevance and applicability of these data to low level pediatric Pb poisoning. Thus, these data suggest that alterations in rod sensitivity and temporal processing may occur in children exposed to low levels of lead during perinatal development.

Animals↗