Regional distribution of citrate synthase and lactate dehydrogenase isoenzymes in the bovine heart

Biochemical and Morphological Alterations in Hearts of Copper-Deficient Bovines

Copper deficiency is an important disease of cattle that produces several clinical signs and lesions, due to alterations in copper-dependent enzymes. One of the organs affected by this deficiency is the heart (falling disease), but nevertheless, these cardiac lesions have not been extensively studied in bovines. The aim of this work was to propose a possible pathogenic mechanism for cardiac lesions in cattle affected by copper deficiency. Because of the possible existence of oxidative distress caused by low levels of copper-zinc-superoxide dismutase and cytochrome oxidase, ultrastructural and histological lesions have been evaluated in the heart of bovines in which a Cu deficiency had been induced using high molybdenum and sulfur levels in the diet. Our results indicated that copper deficiency produces significant damage in myocardium with high levels of lipid oxidation and a significant reduction in copper-zinc-superoxide dismutase activity leading to an oxidative distress situation. However, cytochrome oxidase activity was not significantly reduced. Histological observation revealed a significant increase in the amount of connective tissue, enlarged basement membranes of myocytes, and numerous Anichkov cells, in the hearts of deficient animals. Ultrastructural observation showed a significant enhancement in the mitochondrial volume density, with presence of lesions such as swelling and cristae disruption. We conclude that copper deficiency in bovines causes morphological lesions in the heart due to an oxidative damage produced by copper-dependent enzyme alterations.

Aging impairs flow-induced dilation in coronary arterioles: role of NO and H(2)O(2)

Aging contributes significantly to the development of cardiovascular disease and is associated with elevated production of reactive oxygen species (ROS). The beneficial effects of nitric oxide (NO)-mediated vasodilation are quickly abolished in the presence of ROS, and this effect may be augmented with aging. We previously demonstrated an age-induced impairment of flow-induced dilation in rat coronary arterioles. Therefore, the purpose of this study was to determine the effects of O(2)(-) scavenging, as well as removal of H(2)O(2), the byproduct of O(2)(-) scavenging, on flow-mediated dilation in coronary resistance arterioles of young (4 mo) and old (24 mo) male Fischer 344 rats. Flow increased NO and H(2)O(2) production as evidenced by enhanced diaminofluorescein and dichlorodihydrofluorescein fluorescence, respectively, whereas aging reduced flow-induced NO and H(2)O(2) production. Endothelium-dependent vasodilation was evaluated by increasing intraluminal flow (5-60 nl/s) before and after treatment with the superoxide dismutase mimetic Tempol (100 muM), the H(2)O(2) scavenger catalase (100 U/ml), or Tempol plus catalase. Catalase reduced flow-induced dilation in both groups, whereas Tempol and Tempol plus catalase diminished vasodilation in young but not old rats. Tempol plus deferoxamine (100 muM), an inhibitor of hydroxyl radical formation, reversed Tempol-mediated impairment of flow-induced vasodilation in young rats and improved flow-induced vasodilation in old rats compared with control. Immunoblot analysis revealed increases in endogenous superoxide dismutase, catalase, and nitrotyrosine protein levels with aging. Collectively, these data indicate that NO- and H(2)O(2)-mediated flow-induced signaling decline with age in coronary arterioles and that elevated hydroxyl radical formation contributes to the age-related impairment of flow-induced vasodilation.

Myocardial lactate dehydrogenase subunit ratio in cardiac allograft recipients

BACKGROUND

Allograft coronary artery disease (CAD) is a major long-term complication in heart transplanted patients. However, the metabolic basis of allograft CAD remains to be fully elucidated. We analyzed the lactate dehydrogenase heart (H) and muscle (M) isoenzyme pattern in endomyocardial biopsy specimens and the evolution of the H/M ratio to test whether changes in this ratio could be the earliest manifestation of allograft CAD.

METHODS

Twenty-four heart transplant recipients were followed up for 12 months. Endomyocardial biopsy was performed at 1, 2, 3, 6, and 12 months after transplantation. Lactate dehydrogenase 1 through 5 isoenzymes were separated by electrophoresis, and the H/M ratio was calculated. Two groups of patients were identified: group 1 (n = 20), patients without allograft CAD; and group 2 (n = 4), patients with poor outcome (three deaths, 1 case of low cardiac output) and angiographic and histologic evidence of allograft CAD.

RESULTS

Both groups had similar H/M baseline values. The H/M ratio was higher (p = 0.01) in group 1 at 6 months (3.48 +/- 0.64 versus 2.17 +/- 0.43) and 12 months (3.76 +/- 0.92 versus 2.18 +/- 0.45) when compared with group 2. The H/M ratio increased from 2.78 +/- 0.89 at 1 month to 3.76 +/- 0.92 at 12 months (p = 0.02) in group 1 and decreased in group 2 (2.86 +/- 0.49 versus 2.18 +/- 0.45; not significant).

CONCLUSIONS

Changes in H/M ratio reflect an anaerobic shift in the lactate dehydrogenase isoenzyme composition and can be taken as an early indicator of allograft CAD.

Local blood flow is not linked to lactate within single rabbit skeletal muscles

A marked regional distribution in blood flow within single skeletal muscles on a non-microvascular level, i.e. at the level of large arterioles or small arteries, is present in dog, cat and rabbit. The mechanism for this perfusion pattern is not known. The goal of the present study was to see if regional blood flow was correlated to regional lactate metabolism. Anesthetized rabbits were studied. Blood flow to 0.25 g muscle samples was measured with microspheres whereas lactate content and lactate dehydrogenase activity were determined in extracts of these samples. No correlation was detected between regional blood flow and regional lactate or lactate dehydrogenase either at rest or during exercise hyperemia. Expressed as the coefficient of variation (CVc), regional blood flow showed a marked scatter, the CVc ranged from 0.32 to 0.35. The corresponding CVc for both lactate and lactate dehydrogenase activity ranged from 0.16 to 0.19. It is concluded that regional blood flow is not correlated to regional lactate metabolism. The regional distribution in blood flow was markedly more uneven than that for lactate content and for lactate dehydrogenase activity.

Evidence for long-term fluctuations in regional blood flow within the rabbit left ventricle

The regional distribution of coronary perfusion within the left ventricle is markedly heterogenous. The perfusion pattern is composed of both spatial and temporal variations in perfusion among single myocardial samples. Previous investigators have mostly studied short-term (< 1 min) temporal variability. The aim of this study was to quantify long-term fluctuations in perfusion to single samples within the rabbit left ventricle. Coronary perfusion was estimated from the deposition of microspheres in myocardial samples (range 32-96 mg). Two batches of microspheres were infused either simultaneously or sequentially over specified periods of time. The paired values for regional perfusion were compared and Kendalls correlation coefficient (tau) calculated. The assumption being that the lower tau, the higher degree of temporal perfusion variability was present. The tau for paired values of regional myocardial perfusion based on two sequential infusions lasting either 10 s, 5, 10 or 30 min, averaged 0.40, 0.55, 0.80 and 0.80, respectively. No difference was detected between awake and anaesthetized animals. The tau for two simultaneous infusions averaged 0.95 irrespective of the duration of the infusion, indicating negligible methodological error. The coefficient of variation for spatial perfusion heterogeneity ranged from 0.3 to 0.4 irrespective of the infusion duration. The findings suggest that regional coronary vasomotion is characterized by a wide range of cycle times, some of which have cycle times of more than 30-min duration. Although part of the regional perfusion heterogeneity was due to long-term fluctuations in perfusion, temporal variations with cycle times less than 5 and 10 min, respectively, were more prominent.

Uneven perfusion within single cat muscles: nitric oxide and citrate synthase play no role

There is an unexplained, marked regional heterogeneity in perfusion within single skeletal muscles both in dogs and rabbits. We asked if a similar distribution of perfusion was present within cat muscles. If present, we wanted to assess the possible roles of nitric oxide (NO) mediated vasodilation and citrate synthase (CS) activity for the regulation of this perfusion pattern. Perfusion was determined in 0.25 g regions within the gastrocnemius muscles by trapping of microspheres. We studied awake or anesthetized cats before and during inhibition of NO-formation using N-monomethyl-L-arginine. The CS activity was determined in homogenates of these regions. The coefficient of variation corrected for the Poisson distribution of microspheres (CVc) for the regional perfusion averaged 0.39. Despite a 25% reduction in perfusion to the whole muscles as compared to control, the uneven distribution of perfusion was not affected by blocking NO formation. Regional perfusion was not correlated to regional CS activity. Even if the regional distribution of CS activity also showed a scatter, mean coefficient of variation corrected for methodological error = 0.20, it was markedly less than that for perfusion. We conclude that neither NO vasodilation nor CS activity play an important role in the regulation of the regional perfusion pattern within single cat muscles.