Lactate dehydrogenase activity and isoform distribution in the rat urinary bladder: effects of outlet obstruction and its removal

Molecular and Morphological Characteristics of the De-Obstructed Rat Urinary Bladder—An Update

Many patients with outlet obstruction secondary to prostatic enlargement have lower urinary tract symptoms (LUTSs) and an increased frequency of micturition. The standard treatment is transurethral resection of the prostate (TURP), which alleviates obstruction and symptoms. However, after TURP, 20–40 percent of patients continue to experience LUTSs. The aim of the present study in rats was to identify the mechanisms that do not normalize after the removal of the obstruction and that could explain the persisting symptoms. We had microarray data from control, obstructed, and de-obstructed female rat bladders, which made it possible to study 14,553 mRNA expressions. We also had a bank of electron micrographs from similar detrusors. Microarrays: There were significant differences between the control and obstructed bladders for 1111 mRNAs. The obstructed and de-obstructed bladders differed significantly for 1059 mRNAs. The controls and the de-obstructed bladders differed significantly for 798 mRNAs. We observed many mRNAs that were increased in the obstructed bladder and then decreased to control levels after de-obstruction, and many mRNAs that were decreased in the obstructed bladder and then increased following de-obstruction. mRNAs that were significantly higher or lower in the de-obstructed bladder than in the control bladder were also found. Ultrastructure: The detrusor cells in the obstructed bladders had cross-sectional areas that were much larger than those in the controls. The control cells had smooth outlines and similar cross-sectional areas. The de-obstructed detrusor cells had larger cross-sectional areas than the controls, as well as corrugated surfaces. The cell areas varied, suggesting that the shrinkage of the de-obstructed cells was not even. We did not find any points of contact of the gap junction plaque type between the detrusor cells. There were abundant finger-like processes between the detrusor cells in the obstructed and in de-obstructed bladders, which were only occasionally found in the control detrusors. They are the only possible localization for gap junction channels. The de-obstructed rat bladder is not an organ with properties intermediate between those of the control and obstructed bladders. Instead, de-obstructed bladders have gene expressions, morphologies, and functional properties of the individual cells and their organization, which make them distinctly different from both control and obstructed bladders.

HIF-mediated metabolic switching in bladder outlet obstruction mitigates the relaxing effect of mitochondrial inhibition

Prior work demonstrated increased levels of hypoxia-inducible factor-1α (HIF-1α) in the bladder following outlet obstruction, associated with bladder growth and fibrosis. Here we hypothesized that HIF induction in outlet obstruction also switches energetic support of contraction from mitochondrial respiration to glycolysis. To address this hypothesis, we created infravesical outlet obstruction in female Sprague-Dawley rats and examined HIF induction and transcriptional activation. HIF-1α increased after 6 weeks of outlet obstruction as assessed by western blotting and yet transcription factor-binding site analysis indicated HIF activation already at 10 days of obstruction. Accumulation HIF-2α and of Arnt2 proteins were found at 10 days, providing an explanation for the lack of correlation between HIF-1α protein and transcriptional activation. HIF signature targets, including Slc2a1, Tpi1, Eno1 and Ldha increased in obstructed compared with sham-operated bladders. The autophagy markers Bnip3 and LC3B-II were also increased at 6 week of obstruction, but electron microscopy did not support mitophagy. Mitochondria were, however, remodeled with increased expression of Cox4 compared with other markers. In keeping with a switch toward glycolytic support of contraction, we found that relaxation by the mitochondrial inhibitor cyanide was reduced in obstructed bladders. This was mimicked by organ culture with the HIF-inducer dimethyloxalylglycine, which also upregulated expression of Ldha. On the basis of these findings, we conclude that HIF activation in outlet obstruction involves mechanisms beyond the accumulation of HIF-1α protein and that it results in a switch of the energetic support of contraction to anaerobic glycolysis. This metabolic adaptation encompasses increased expression of glucose transporters and glycolytic enzymes combined with mitochondrial remodeling. Together, these changes uphold contractility when mitochondrial respiration is limited.

Role of angiogenesis in bladder response to partial outlet obstruction

Benign prostatic hyperplasia (BPH) is a disease that has its etiology in the abnormal growth of the adult human prostate gland that accompanies the aging process in men. The symptomatic presentation of this disease, however, is related largely to degenerative changes in the bladder that occur as a result of the increasing urethral resistance and partial bladder outlet obstruction (PBOO) caused by the growing prostate gland. BPH is characterized by bladder hypertrophy, significant decreases in urinary flow and compliance, presence of residual urine after voiding, voiding urgency and incontinence (). Obstructed bladder dysfunction secondary to BPH is a slow, progressive disease that is so strongly associated with human aging that it is an expected occurrence of the male aging process. Although the symptoms of BPH are usually not life threatening, they effect an extremely negative quality of life for men who suffer from them. However, many men delay seeking medical treatment for early BPH since bladder function can remain relatively normal as the hypertrophying bladder initially compensates for the progressive increase in urethral resistance caused by prostatic obstruction. The limited changes in micturition pressure and flow characteristics that occur during compensated function are not usually disabling enough to motivate seeking medical attention, which, often, is not sought until the symptoms become typical of advanced disease. Recent advances in detection methods enable identification of patients with significant BPH during compensation before the bladder becomes dysfunctional (decompensated). A more complete understanding of the disease processes that underlie the loss of bladder function associated with BPH might enable the development of treatments that better protect these early-stage BPH patients from the more debilitating aspects of the disease. This review updates the understanding of obstructive bladder dysfunction via the use of animal models.

Gender-related neuronal and smooth muscle damage of guinea pig isolated urinary bladder from anoxia-glucopenia and reperfusion injury and its relationship to glycogen content

AIMS

To investigate the effects of anoxia and glucopenia (A-G) on both male and female guinea pig urinary bladder.

METHODS

In whole bladders superfused with oxygenated Krebs' solution, intrinsic nerves underwent electrical field stimulation (EFS) and smooth muscle stimulated with carbachol, ATP, and high potassium. The effect of 1, 2, or 3 hr A-G on the contractile response and the ensuing recovery in Krebs' solution, was monitored. Glycogen content in male and female urinary bladders was also measured.

RESULTS

Under different stimuli male urinary bladder proved to contract more efficiently than female organ. After 1 hr A-G the EFS response of male urinary bladder was virtually abolished and returned to 60% of control response in the recovery phase; in female bladder the EFS responses fully recovered during the reperfusion phase. Full recovery of the response to carbachol, ATP, and high potassium stimulations was observed in both genders. A-G had to be extended to 2 hr to cause smooth muscle impairment (higher in male than in female) and a neuronal impairment in female urinary bladders. When 2-deoxyglucose (2-DG), an inhibitor of glycolysis, was added during 1 hr A-G, both neuronal and smooth muscle damages were significantly enhanced in male, as well as, though to a lesser extent, in female bladder. A significantly higher glycogen content was observed in female as compared to male bladders, which was inversely related with the duration of exposure to A-G.

CONCLUSIONS

The higher resistance of female urinary bladder to A-G/reperfusion, can be partly ascribed to the higher glycogen content.

Improved performance of column chromatography by arginine: Dye-affinity chromatography

Arginine has been effectively used in various column chromatographies for improving recovery and resolution, and suppressing aggregation. Here, we have tested the effectiveness of arginine as an eluent in dye-affinity column chromatography using Blue-Sepharose, which binds enzymes requiring adenyl-containing cofactors (e.g., NAD). A common eluent, NaCl, showed a broad elution peak with low recovery of lactate dehydrogenase, at most approximately 60% using 2M salt. The recovery decreased as the NaCl concentration was either decreased or increased; i.e., the recovery was maximum at 2M. On the contrary, addition of arginine to the eluent resulted in more than 80% recovery above 0.5M and the recovery was nearly independent of the arginine concentration. The elution peak was much sharper with arginine, leading to elution of more concentrated protein solution. Successful elution of proteins bound to the ATP-agarose resins by arginine was also described.

Effect of anoxia-glucopenia and re-superfusion on intrinsic nerves of mammalian detrusor smooth muscle: Importance of glucose metabolism

AIMS

To investigate the effect of anoxia/glucopenia and re-superfusion on intrinsic nerves in the mammalian urinary bladder.

METHODS

Strips of detrusor smooth muscle were dissected from monkey and human urinary bladder and mounted for tension recording in organ baths superfused with Krebs solution. Human, monkey, and guinea-pig urinary bladders were treated to evaluate glycogen contents by a biochemical method.

RESULTS

Detrusor strips from both monkeys and humans had to be exposed to anoxia-glucopenia for up to 2-2.5 hr to observe a progressive decline in the response to electrical field stimulation (EFS) of the intrinsic nerves, at variance with guinea-pig detrusor strips. In contrast, the response to direct activation of the smooth muscle with carbachol remained almost unaltered. Incubation of human and monkey detrusor strips with 2-deoxyglucose (2-DG) during 1 hr anoxia-glucopenia, however, caused a marked damage to the intrinsic nerves. The glycogen contents of both human detrusor specimens and monkey urinary bladders were 2.0- and 1.4-fold higher, respectively, than that found in guinea-pig urinary bladder; furthermore, untreated monkey detrusor sections showed a greater number of glycogen granules as compared to those subjected to anoxia-glucopenia and re-superfusion. In guinea-pig and in monkey detrusor sections glycogen granules were found in smooth muscle cells but not in neurons of intramural ganglia.

CONCLUSIONS

A higher susceptibility of guinea-pig as compared to monkey and human nerves has been demonstrated; it is suggested that anaerobic glucose metabolism during anoxia-glucopenia is crucial for the functional recovery of detrusor intrinsic nerves from damage caused by anoxia-glucopenia and re-superfusion.

Urinary bladder contraction and relaxation: physiology and pathophysiology

The detrusor smooth muscle is the main muscle component of the urinary bladder wall. Its ability to contract over a large length interval and to relax determines the bladder function during filling and micturition. These processes are regulated by several external nervous and hormonal control systems, and the detrusor contains multiple receptors and signaling pathways. Functional changes of the detrusor can be found in several clinically important conditions, e.g., lower urinary tract symptoms (LUTS) and bladder outlet obstruction. The aim of this review is to summarize and synthesize basic information and recent advances in the understanding of the properties of the detrusor smooth muscle, its contractile system, cellular signaling, membrane properties, and cellular receptors. Alterations in these systems in pathological conditions of the bladder wall are described, and some areas for future research are suggested.

Smooth, slow and smart muscle motors

Smooth muscle is a slow and economical muscle with a large variability in contractile properties. This review describes results regarding the relation between expression of myosin isoforms and the contraction of smooth muscle. The focus of the review is on studies of the organised contractile system in the smooth muscle tissue. The role of the myosin heavy chain variants formed by alternative splicing in the myosin heavy chain tail (SM1, SM2 isoforms) and head (SM-A SM-B isoforms) regions, as well as the role of essential light chains (LC17a, LC17b isoforms) for the variability of contractile properties are discussed. Smooth muscle also has the ability to alter its contractile properties in response to altered functional demands in vivo, e.g. during hypertrophic growth of urinary bladder, intestine, uterus and vessels and in response to altered hormone levels. These alterations involve changes in myosin expression and altered contractile kinetics. Non-muscle myosin has been shown to have a contractile function in some smooth muscle tissues and recent data on the kinetic properties of non-muscle myosin filaments in smooth muscle tissue are described.

Normal detrusor is more sensitive than hypertrophied detrusor to in vitro ischemia followed by re-oxygenation

Partial outlet obstruction results in marked metabolic as well as contractile alterations. Specifically, the ratio of anaerobic to oxidative metabolism is significantly greater in hypertrophied than normal bladder smooth muscle, lactate dehydrogenase (LDH) and lactic acid production are increased, and the contractile apparatus is altered to allow for metabolically more efficient tension generation. In addition, contractile responses of hypertrophied bladder are apparently more resistant than those of normal bladder to hypoxia. In the current experiment, we studied the effects of in vitro ischemia (hypoxia + substrate deprivation) followed by an in vitro model of reperfusion (re-oxygenation + substrate replacement) on contractile responses of normal and hypertrophied urinary bladder strips. We used repetitive field stimulation (FS) during the hypoxic period as a model for hyperreflexia. The purpose of the current study was to compare the responses of normal and hypertrophied bladder smooth muscle to repetitive stimulation in the presence of in vitro ischemia followed by re-oxygenation and substrate replacement. Thirty-two rats were separated into four groups of eight each. The rats in groups 1 and 3 were subjected to partial outlet obstruction. Two weeks later, all rats were anesthetized; their bladders were isolated and cut into four strips. Each strip was mounted in an isolated bath, and after 1-hour incubation in Tyrode's solution containing glucose (in the presence of O(2)), contractile responses to FS, carbachol, and KCl were determined. After this first set of stimulations, the strips were incubated without glucose and in the presence of N(2) for 30 minutes and 1 hour (groups 1 and 2); and for 2 and 4 hours (groups 3 and 4). For groups 1 and 2, the tissues were stimulated at 5-minute intervals with FS at 32 Hz, 1-millisecond duration, 3-second trains (in vitro model of hyperreflexia). For groups 3 and 4, no stimulations were performed during the ischemic period. At the end of the ischemic period, all strips were washed and incubated for 1 hour in the presence of O(2) and with glucose. At the end of this incubation, all strips received a second set of stimulations. a) Partial outlet obstruction resulted in a significant increase in bladder weight. b) Responses to in vitro ischemia: After in vitro ischemia, contractile responses of both normal and hypertrophied tissues to FS were reduced to a significantly greater degree than were responses to carbachol and KCl. The rate of development of contractile dysfunction was significantly greater in normal bladder tissue strips than in hypertrophied bladder strips. c) Responses to repetitive stimulation: The rate of development of contractile dysfunction was significantly greater in all strips subjected to repetitive stimulation than in those not repetitively stimulated; in addition, normal bladder strips were more sensitive than hypertrophied strips to hypoxia and substrate deprivation-induced contractile dysfunction. The rate of contractile failure induced by in vitro ischemia followed by re-oxygenation and substrate replacement was significantly greater for normal bladder strips than for hypertrophied bladder strips. These results indicate that, after partial outlet obstruction, the hypertrophied tissue is more resistant than normal tissue to hypoxia and substrate deprivation.

The effect of bladder outflow obstruction on detrusor blood flow changes during the voiding cycle in conscious pigs

PURPOSE

We monitored detrusor blood flow in pigs with bladder outflow obstruction.

MATERIALS AND METHODS

Partial urethral obstruction was created in 9 immature, female large white pigs with an implanted ring, and 10 normal animals were used for comparison. Urodynamic parameters and detrusor blood flow were measured using chronically implanted access catheters and laser Doppler fibers. Repeated recordings were made from each animal while it was lightly sedated.

RESULTS

The animals with implanted rings developed prolonged, high pressure voiding contractions in association with poor urinary flow, indicating bladder outflow obstruction, and had evidence of detrusor instability. In obstructed and normal animals detrusor blood flow was maintained during bladder filling. Elevated detrusor pressure during voiding significantly decreased blood flow to similar levels in each group. The duration of the ischemic period was much greater in obstructed animals.

CONCLUSIONS

Bladder outflow obstruction is associated with repeated episodes of prolonged detrusor ischemia which may account for the biochemical and neuronal alterations in such bladders.

Effect of partial outlet obstruction on 14C-adenine incorporation in the rabbit urinary bladder

Bladder outlet obstruction induces severe changes in urinary bladder function and metabolism. These changes are characterized by significant reductions in the ability of the in vitro whole bladder to generate pressure and to empty. Metabolically, partial outlet obstruction induces a shift from oxidative to anaerobic metabolism. The decreased oxidative metabolism is mediated in part by significant decreases in mitochondrial substrate metabolism, which in turn is correlated with decreased activity of 2 important mitochondrial enzymes: citrate synthase and malate dehydrogenase. The present study was designed to evaluate mitochondrial function by studying the incorporation of 14C-adenine into high-energy phosphates (ATP, AMP, and ADP). Mild partial outlet obstructions were created by surgically placing silk ligatures loosely around the bladder neck. The results of these studies demonstrate that after 60 min incubation in oxygenated medium containing glucose + 1uCi14C-adenine, 1) There was no significant differences in the total AMP, ADP, and ATP concentrations measured in bladders taken from controls, 7- and 14-day obstructed rabbits; 2) there was no effect of obstruction on either the concentration of 14C-AMP in the tissue or in the ratio of hot to cold AMP; and 3) there was a 50% decrease in the concentration of 14C-ADP and a 70% decrease in the concentration of 14C-ATP in the bladder smooth muscle obtained from obstructed tissue (from both 7- and 14-day obstructions) compared to concentration in the control bladder smooth muscle. These results confirm the previous finding that obstruction did not reduce the rate of incorporation of adenine to AMP within the obstructed bladder smooth muscle and extends these studies to identify a significant reduction in the synthesis of both ADP and ATP. These results support the hypothesis that partial outlet obstruction induce a major dysfunction in mitochondrial function, both in the ability to oxidize substrates and in the ability to generate ATP.

The effect of bladder outlet obstruction on tissue oxygen tension and blood flow in the pig bladder

OBJECTIVE

To investigate the effect of partial bladder outlet obstruction on detrusor blood flow and oxygen tension (PdetO2) in female pigs.

MATERIALS AND METHODS

Detrusor-layer oxygen tension and blood flow were measured using oxygen-sensitive electrode and radiolabelled microsphere techniques in five female Large White pigs with a partial urethral obstruction and in five sham-operated controls. The effects of chronic outlet obstruction on bladder weight, and cholinergic nerve density and distribution, are also described.

RESULTS

In the obstructed bladders, blood flow and oxygen tension were, respectively, 54.9% and 74.3% of control values at low bladder volume, and 47.5% and 42.5% at cystometric capacity. Detrusor blood flow declined by 27.8% and 37.5% in the control and obstructed bladders, respectively, as a result of bladder filling, whilst PdetO2 did not decrease in the controls, but fell by 42.7% in the obstructed bladders. Bladder weight increased whilst cholinergic nerve density decreased in the obstructed animals.

CONCLUSION

In pigs with chronic bladder outlet obstruction, blood flow and oxygen tension in the detrusor layer were lower than in control animals. In addition, increasing detrusor pressure during filling caused significantly greater decreases in blood flow and oxygen tension in the obstructed than in the control bladders.

Effects of glucose deprivation on the contractile response of the rabbit bladder to repetitive stimulation

The urinary bladder requires an adequate energy supply to maintain contractile function. The primary metabolic fuel is glucose. Through glycolysis and oxidative phosphorylation, high energy phosphates are generated, which in turn supply the metabolic energy for the contractile activities of the urinary bladder. The aim of this study was to determine the effects of glucose deprivation and recovery from glucose deprivation on the phasic and tonic components of the contractile responses of rabbit bladder strips to field stimulation, bethanechol, and KCl. The results can be summarized as follow: In response to glucose deprivation, (1) the tonic responses to field stimulation, bethanechol, and KCl all decreased at a significantly greater rate than the phasic responses; (2) the phasic and tonic responses to field stimulation were both reduced to less than 10% of control within 70 minutes of initiating glucose deprivation; (3) the tonic responses to bethanechol and KCI were reduced to approximately 10% of control within 180 minutes whereas the phasic responses remained stable at 40 and 30%, respectively; and (4) glucose replacement stimulated a rapid and nearly complete recovery of the phasic and tonic components of the responses to field stimulation, bethanechol, and KCI. These results indicate that the tonic responses to all forms of stimulation are more sensitive to glucose deprivation than the phasic responses.

Lactate dehydrogenase activity and isoform distribution in the rat pelvic ganglion: effects of diabetes and bladder outlet obstruction

We have previously shown that the intramural motor nerves in the rat bladder can function in anoxic conditions. The present study aims to explore the distribution and activity of lactate dehydrogenase (LDH), the key enzyme for ATP generation in anoxia. The activity and isoform distribution pattern of LDH was studied in pelvic ganglia from male and female rats. A histochemical investigation showed that the LDH activity was intense in the ganglion cells, and weak in the other tissue components (nerve bundles, connective tissue). The male pelvic ganglion weighted 55% more than the female pelvic ganglion, the enzyme activity per unit ganglion weight was 60% higher and the total LDH activity was 155% higher. The isoform distribution was similar, with M4 being dominant isoform, followed by M3H. Infravesical outlet obstruction in the female rat induced a threefold increase in ganglion weight, and the total LDH activity increased twofold. In this hypertrophic female ganglion a decreased relative amount of M4, and an increased amount of MH3, was found. Diabetes in the male rat had no effect on ganglion weight or its contents and isoform distribution of LDH.