Cystometric changes in alloxan diabetic rats: evidence for functional and structural correlates of diabetic autonomic neuropathy

Methylglyoxal and Advanced Glycation End Products (AGEs): Targets for the Prevention and Treatment of Diabetes-Associated Bladder Dysfunction?

Methylglyoxal (MGO) is a highly reactive α-dicarbonyl compound formed endogenously from 3-carbon glycolytic intermediates. Methylglyoxal accumulated in plasma and urine of hyperglycemic and diabetic individuals acts as a potent peptide glycation molecule, giving rise to advanced glycation end products (AGEs) like arginine-derived hydroimidazolone (MG-H1) and carboxyethyl-lysine (CEL). Methylglyoxal-derived AGEs exert their effects mostly via activation of RAGE, a cell surface receptor that initiates multiple intracellular signaling pathways, favoring a pro-oxidant environment through NADPH oxidase activation and generation of high levels of reactive oxygen species (ROS). Diabetic bladder dysfunction is a bothersome urological complication in patients with poorly controlled diabetes mellitus and may comprise overactive bladder, urge incontinence, poor emptying, dribbling, incomplete emptying of the bladder, and urinary retention. Preclinical models of type 1 and type 2 diabetes have further confirmed the relationship between diabetes and voiding dysfunction. Interestingly, healthy mice supplemented with MGO for prolonged periods exhibit in vivo and in vitro bladder dysfunction, which is accompanied by increased AGE formation and RAGE expression, as well as by ROS overproduction in bladder tissues. Drugs reported to scavenge MGO and to inactivate AGEs like metformin, polyphenols, and alagebrium (ALT-711) have shown favorable outcomes on bladder dysfunction in diabetic obese leptin-deficient and MGO-exposed mice. Therefore, MGO, AGEs, and RAGE levels may be critically involved in the pathogenesis of bladder dysfunction in diabetic individuals. However, there are no clinical trials designed to test drugs that selectively inhibit the MGO-AGEs-RAGE signaling, aiming to reduce the manifestations of diabetes-associated bladder dysfunction. This review summarizes the current literature on the role of MGO-AGEs-RAGE-ROS axis in diabetes-associated bladder dysfunction. Drugs that directly inactivate MGO and ameliorate bladder dysfunction are also reviewed here.

Normalization of organ bath contraction data for tissue specimen size: does one approach fit all?

Organ bath experiments are a key technology to assess contractility of smooth muscle. Despite efforts to standardize tissue specimen sizes, they vary to a certain degree. As it appears obvious that a larger piece of tissue should develop greater force, most investigators normalize contraction data for specimen size. However, they lack agreement which parameter should be used as denominator for normalization. A pre-planned analysis of data from a recent study was used to compare denominators used for normalization, i.e., weight, length, and cross-sectional area. To increase robustness, we compared force with denominator in correlation analysis and also coefficient of variation with different denominators. This was done concomitantly with urinary bladder strips and aortic rings and with multiple contractile stimuli. Our urinary bladder data show that normalization for strip weight yielded the tightest but still only moderate correlation (e.g., r² = 0.3582 for peak carbachol responses based on 188 strips). In aorta, correlations were even weaker (e.g., r² = 0.0511 for plateau phenylephrine responses normalized for weight based on 200 rings). Normalization for strip size is less effective in reducing data variability than previously assumed; the normalization denominator of choice must be identified separately for each preparation.

Prunella vulgaris L. active components and their hypoglycemic and antinociceptive effects in alloxan-induced diabetic mice

Prunella vulgaris L. (Lamiaceae) (PV) is a herbaceous plant traditionally utilized in management of diabetes and it has immunomodulatory activity. In this study, acute and subchronic antidiabetic, in-vivo antioxidant and antinociceptive effects of PV were evaluated in alloxan-induced type 1 diabetes (T1D) in a mouse model. Bio-guided fractionation, isolation, RP-HPLC, and ¹H and ¹³C NMR identification of the active components responsible for PV effects were determined. RP-HPLC analysis showed that PV contained rosmarinic acid (RA) 4.5%, caffeic acid (CA) 9.8% and p-coumaric acid (pCA) 11.6%. Bio-guided fractionation showed that PV most active fraction was rich in caffeic acid, hence named, caffeic acid-rich fraction (CARF). RP-HPLC, and ¹H and ¹³C NMR experiments showed that CARF contained CA (93.4%) and RA (6.6%). CARF reduced blood glucose levels and improved in-vivo oxidative-stress. It also inhibited the carbohydrate-hydrolyzing enzymes (alpha-amylase and alpha-glucosidase) and reduced HbA1c levels more significantly (p≤0.05) than that of PV and equivalent amounts of CA or RA. For longer times, CARF had significantly (p≤0.05) increased serum-insulin, ameliorated thermal hyperalgesia and tactile allodynia more significantly (p≤0.05) than the effects of PV and equivalent amounts of CA or RA. Moreover, the tested compounds showed potential restoration of the lipid peroxide levels. Consequently, CARF and PV observed increase in serum-insulin, attenuation of alpha-amylase and alpha-glucosidase, and their antioxidant potentials might be responsible for their antidiabetogenic and antinociceptive properties. In conclusion, CARF isolated from PV could be a potential therapeutic agent to ameliorate T1D and related complications.

Functional and biochemical characteristics of urinary bladder muscarinic receptors in long-term alloxan diabetic rats

OBJECTIVE

To re-examine the function of the urinary bladder in vivoas well as to determine the functional and biochemical characteristics of bladder muscarinic receptors in long-term alloxan-induced diabetes rats.

METHODS

Two-month-old male Wistar rats were injected with alloxan and the animals showing blood glucose levels >300mg/dL together with age-paired untreated animals were kept for 11 months. Body weight, bladder weight, blood glucose, and urinary volume over a period of 24 hours were determined in both groups of animals. A voiding cystometry in conscious control and diabetic rats was performed to determine maximal micturition pressure, micturition contraction interval and duration as well as voided and post-voiding residual volume. In addition, concentration-response curves for bethanechol in isolated bladder strips, as well as [3H]-N methyl-scopolamine binding site characteristics in bladder homogenates were determined.

RESULTS

Mean bladder weight was 162.5±21.2mg versus 290±37.9mg in control and treated animals, respectively (p<0.05). Micturition contraction amplitude (34.6±4.7mmHg versus 49.6±2.5mmHg), duration (14.5±1.7 seconds versus 23.33±4.6 seconds) and interval (87.5±17.02 seconds versus 281.11±20.24 seconds) were significantly greater in alloxan diabetic rats. Voided urine volume per micturition contraction was also significantly higher in diabetic animals. However the post-voiding residual volume was not statistically different. Bethanechol potency (EC50 3µM versus 5µM) and maximal effect (31.2±5.9g/g versus 36.1±6.8g/g) in isolated bladder strips as well as number (169±4fmol/mg versus 176±3fmol/mg protein) and affinity (0.69±0.1nM versus 0.57±0.1nM) of bladder muscarinic receptors were also not statistically different.

CONCLUSION

Bladder function in vivo is altered in chronic alloxan-induced diabetes rats without changes in functional and biochemical characteristics of bladder muscarinic receptors.

Purinergic signalling in the urinary tract in health and disease

Purinergic signalling is involved in a number of physiological and pathophysiological activities in the lower urinary tract. In the bladder of laboratory animals there is parasympathetic excitatory cotransmission with the purinergic and cholinergic components being approximately equal, acting via P2X1 and muscarinic receptors, respectively. Purinergic mechanosensory transduction occurs where ATP, released from urothelial cells during distension of bladder and ureter, acts on P2X3 and P2X2/3 receptors on suburothelial sensory nerves to initiate the voiding reflex, via low threshold fibres, and nociception, via high threshold fibres. In human bladder the purinergic component of parasympathetic cotransmission is less than 3 %, but in pathological conditions, such as interstitial cystitis, obstructed and neuropathic bladder, the purinergic component is increased to 40 %. Other pathological conditions of the bladder have been shown to involve purinoceptor-mediated activities, including multiple sclerosis, ischaemia, diabetes, cancer and bacterial infections. In the ureter, P2X7 receptors have been implicated in inflammation and fibrosis. Purinergic therapeutic strategies are being explored that hopefully will be developed and bring benefit and relief to many patients with urinary tract disorders.

Chapitre E - Troubles vésico-sphinctériens et diabète sucré

Diabetic neuropathy can induce multi-organ functional disease including lower urinary tract dysfunction. After a review of the various neurological lesions associated with diabetes mellitus, the authors describe the voiding disorders observed in diabetics and their specificity. These disorders, usually characterized by a large, flaccid, underactive bladder, must always be interpreted as a function of other diseases of the male or female pelvis that alter an often precarious balance. The management problems raised by this neuropathy are related to the fact that it may not be correctly diagnosed prior to a surgical procedure, for example. A better knowledge of the risk factors and natural history of diabetic bladder must therefore be promoted.

Effects of fidarestat, an aldose reductase inhibitor, on nerve conduction velocity and bladder function in streptozotocin-treated female rats

The effects of fidarestat, an aldose reductase inhibitor (ARI), were assessed on nerve conduction velocity (NCV) in somatic nerves and on multiple measures of bladder function in rats made hyperglycemic with streptozotocin (STZ) and in age-matched controls. Nerve conduction velocity was recorded at baseline and at 10, 20, 30, and 50 days after confirmation of the STZ-induced hyperglycemia in all rats (N=47); bladder function was assessed in a representative subset of rats (N=20) at Day 50. Caudal NCV was markedly slowed by STZ, and this effect was significantly reversed by fidarestat. The initial deficit and treatment-related improvement were especially evident for responses driven by high-frequency repetitive stimulation. Of the 11 parameters of bladder activity assessed, four measures-bladder capacity, micturition volume, micturition frequency, and bladder weight-were significantly different in the control and STZ-treated groups. These deficits were not affected by fidarestat. At Day 50, the induced deficits in bladder function were highly correlated with caudal NCV (r values ranging from 0.70 to 0.96; P values ranging from .02 to <.0001). These results suggested that fidarestat improved the slowing of somatic nerve NCV in hyperglycemic rats, but it was not effective in reversing associated bladder dysfunction, in spite of the highly significant correlation between these two diabetes-induced deficits. Possible explanations for this dissociation are discussed.

Temporal differences in bladder dysfunction caused by diabetes, diuresis, and treated diabetes in mice

Diabetic bladder dysfunction is a common complication of diabetes mellitus (DM) with poorly understood natural history. This study examined the temporal changes in bladder function 3, 9, 12, and 20 wk after induction of DM by streptozotocin (STZ) in male C57BL/6 mice compared with that in age-matched diabetic mice treated with insulin, 5% sucrose-induced diuretic mice, and sham-treated control mice. Conscious cystometrograms of mice were examined in addition to the measurements of micturition cycle. Diabetes resulted in decreased body weight. Bladder weight, urine output, bladder capacity, and compliance increased in the DM and diuretic groups. Peak voiding pressure (PVP) increased initially in both DM and diuretic mice. However, in DM mice, PVP dropped dramatically at and after 12 wk. Similar changes in the capacity, compliance, and emptying ability of the bladder were seen during the first 9 wk of the diabetes or diuresis, whereas significant decline in the emptying ability of the bladder was only seen in diabetes after 12 wk of disease in mice. Long-term insulin replacement effectively reversed most changes in bladder function. These results suggest that the transition from a compensated to a decompensated bladder dysfunction occurs 9-12 wk after induction of DM in mice by STZ.

Plasticity of pelvic autonomic ganglia and urogenital innervation

Pelvic ganglia contain a mixture of sympathetic and parasympathetic neurons and provide most of the motor innervation of the urogenital organs. They show a remarkable sensitivity to androgens and estrogens, which impacts on their development into sexually dimorphic structures and provide an array of mechanisms by which plasticity of these neurons can occur during puberty and adulthood. The structure of pelvic ganglia varies widely among species, ranging from rodents, which have a pair of large ganglia, to humans, in whom pelvic ganglion neurons are distributed in a large, complex plexus. This plexus is frequently injured during pelvic surgical procedures, yet strategies for its repair have yet to be developed. Advances in this area will come from a better understanding of the effects of injury on the cellular signaling process in pelvic neurons and also the role of neurotrophic factors during development, maintenance, and repair of these axons.

Gene therapy using replication-defective herpes simplex virus vectors expressing nerve growth factor in a rat model of diabetic cystopathy

Diabetic cystopathy is one of the common complications of diabetes and current therapy is limited. In the present study, the effects of gene therapy, using replication-defective herpes simplex virus type 1 (HSV-1) vectors to deliver and express the nerve growth factor (NGF) gene (HSV-NGF) on tissue NGF levels and bladder function, were evaluated in streptozotocin (STZ)-induced diabetic rats. Diabetic rats exhibited a significant decrease in NGF levels in the bladder and lumbosacral dorsal root ganglia (DRG) detected by enzyme-linked immunosorbent assay and displayed marked bladder dysfunction 12 weeks after STZ injection. In contrast, rats with bladder wall injection of the NGF expression vector 8 weeks after STZ treatment exhibited a significant increase of NGF levels in the bladder and L6 DRG 4 weeks after HSV-NGF injection. Along with the restoration of tissue NGF expression, in metabolic cage studies and cystometry, HSV-NGF-injected rats also showed significantly reduced bladder capacity and postvoid residual volume than diabetic rats injected with the control vector (HSV-lacZ), indicating that voiding function was improved after HSV vector-mediated NGF gene delivery. Thus, HSV vector-mediated NGF gene therapy may prove useful to restore decreased NGF expression in the bladder and bladder afferent pathways, thereby improving hypoactive bladder function in diabetes.

Implications of diabetes mellitus in urology

The incidence of DM is rapidly growing among Americans. DM will rival cancer and heart disease in terms of cost and suffering. The National Institute of Health is tripling the research dollars that are spent on diabetic-related research in an attempt to combat this disease. Urologists are on the front line in the diagnosis and treatment of the complications of DM. The complications of DM that we reviewed in this article, diabetic cystopathy and diabetic ED, can occur in the early stage of DM and often progress in a silent fashion. More awareness and interest are needed to improve our understanding of diabetic complications in urology. Exciting new approaches in the treatment of diabetic cystopathy and ED are being investigated.

Alteration of M(3) subtype muscarinic receptors in the diabetic rat urinary bladder

The M(3) receptor (M(3)-mAChR) is the major muscarinic subtype in the animal bladder responsible for detrusor contraction. The alterations in its protein quantity and biosynthesis during diabetic cystopathy were investigated. 3-month-old male Wistar rats were divided into two groups: (1) 2-week diabetic rats and (2) normoglycemic control rats. Diabetes was induced by a single intravenous injection of 60 mg/kg streptozotocin. The amount of M(3) receptor protein in the rat bladder body tissue was measured by Western immunoblotting using monoclonal antibodies. For determination of M(3) muscarinic receptor mRNA in the bladder tissue, the method of Northern blotting was employed. The results of the Western immunoblotting showed that the amount of M(3)-mAChR protein in the diabetic bladder was significantly increased by about 70.2 +/- 8.5% when compared to the control bladder (p < 0.05, n = 8). Northern blotting demonstrated a 54.7 +/- 6.0% increase of M(3)-mAChR mRNA in the diabetic bladder (p < 0.05, n = 8). The findings of the present study demonstrated an upregulation of M(3)-mAChR biosynthesis in the diabetic urinary bladder. This phenomenon offers an explanation of the increased contractility after muscarinic stimulation of the detrusor muscle of diabetic animals.

Diabetic cystopathy: relationship to autonomic neuropathy detected by sympathetic skin response

PURPOSE

The possible relationship between bladder dysfunction and autonomic neuropathy was investigated in unselected diabetic patients.

MATERIALS AND METHODS

Bladder function was examined by cystometry in 53 unselected diabetic patients and 10 healthy controls. Sympathetic skin response was recorded in 23 of 53 patients and all control subjects to evaluate autonomic neuropathy associated with diabetes, and the results were compared to cystometric findings.

RESULTS

Cystometrograms exhibited significant increases in bladder volume at first desire to void and maximal bladder capacity, and a decrease in detrusor contractility in diabetic patients compared to those in controls. In addition, mean residual urine was significantly larger in diabetic patients than in controls. Among the 53 diabetic patients these bladder dysfunctions were also found in each subset of patients with no sign of retinopathy (33), no subjective urinary symptoms (32) or duration of diabetes less than 1 year (12). In 23 patients in whom sympathetic skin response was measured 12 without sympathetic skin responses had increased residual urine and decreased detrusor contraction pressure. The remaining 11 patients with a lower amplitude of sympathetic skin response and more prolonged latency than controls had a significant decrease in detrusor contraction pressure.

CONCLUSIONS

Bladder dysfunction, characterized by loss of sensation, increased capacity and decreased contractility, was the main observation of diabetic cystopathy regardless of the duration or severity of the disease. The association of bladder dysfunction and autonomic neuropathy detected by the sympathetic skin response might indicate that diabetic cystopathy is a manifestation of peripheral neuropathy induced by diabetes.

Alterations in urinary bladder synaptosomal neurotransmitter concentrations in two-week streptozotocin-induced diabetic rats

Three-month-old male Wistar rats were rendered diabetic with a single intravenous injection of streptozotocin (60 mg/kg body weight). Two weeks after induction of diabetes, synaptosome-rich fractions were prepared from urinary bladder tissue homogenate of the diabetic rats and control rats by differential centrifugation (1000 x g, 17,000 x g and 100,000 x g) with discontinuous sucrose gradient. Synaptosomal acetylcholine, norepinephrine, epinephrine and dopamine were measured by the method of high-performance liquid chromatography. The respective neurotransmitter concentrations for the diabetic rats were 1537.8 +/- 65.3, 4757.7 +/- 361.9, 3720.7 +/- 276.1, and 2447.8 +/- 196.8 pmol/mg synaptosomal protein, respectively; those for the control rats were 338.1 +/- 25.0, 1009.0 +/- 54.6, 645.3 +/- 52.2, and 1426.1 +/- 123.9 pmol/mg protein, respectively. Thus, the synaptosomal concentrations for all the measured neurotransmitters were significantly higher in the diabetic rats (P < 0.05 for each comparison). In conclusion, it has been demonstrated that the vesicle-bound acetylcholine and catecholamines in the synaptosome-rich fraction of the urinary bladder were significantly increased in 2-week diabetic rats. This finding would suggest impaired neurotransmitter release from both the bladder sympathetic and parasympathetic efferent nerve endings in early streptozotocin-induced diabetes.

Factors underlying the increased sensitivity to field stimulation of urinary bladder strips from streptozotocin-induced diabetic rats

1. The responses of bladder strips from control, streptozotocin-diabetic, and sucrose-drinking rats to electrical field stimulation were investigated. Sucrose-drinking rats were included as additional controls because they have enlarged bladders as a result of non-diabetic diuresis. 2. Bladder strips from diabetic rats developed more spontaneous activity than those from the two control groups. Indomethacin reduced the amplitude and frequency of spontaneous contractions suggesting that they resulted from endogenous prostaglandin formation. Tetrodotoxin (TTX) had little effect, while alpha, beta-methylene ATP caused increases in spontaneous activity. 3. Bladder strips from diabetic rats responded to field stimulation with greater contractions than controls in the absence of antagonists as well as in the presence of atropine and alpha, beta-methylene ATP. Increasing TTX concentrations caused a step-wise depression of the contractile response to electrical stimulation which was not affected by preincubation with either atropine or alpha, beta-methylene ATP. 4. Atropine and indomethacin had no effect on strength-duration curves constructed to measure threshold contractile responses to five pulses stimulation. The curves were shifted to the right by both TTX and alpha, beta-methylene ATP, indicating that the responses were neurogenic in nature and at least partially, the result of stimulation of P2-purinoceptors. In the absence of drugs, bladder strips from diabetics responded at lower voltages and pulse widths than those of control and sucrose-drinking rats, suggesting that they were more excitable. 5. The response curve of bladder strips from diabetics to field stimulation at increasing voltage was shifted upwards and to the left compared to strips from control or sucrose-drinking rats. 6. Bladder strips from diabetics responded to stimulation at increasing pulse width with greater responses than those from control or sucrose-drinking rats. At 1.0 ms pulse width, the TTX-resistant response of strips from diabetic rats was still greater than that of the other groups, indicating that a myogenic component was also involved.7. The data suggest that bladder strips from diabetic rats are more excitable than those of control or sucrose-drinking rats. This may result from diabetes-induced decreases in bladder lipid or other membrane changes, and/or be a result of partial depolarization, perhaps related to diabetic neuropathy.

Alterations in neural pathways to the urinary bladder of the rat in response to streptozotocin-induced diabetes

Voiding dysfunction in diabetics has been attributed to a variety of causes including an axonopathy in autonomic pathways to the urinary bladder. The present study was undertaken to determine whether changes occurred in afferent and efferent neurons supplying bladders of streptozotocin (STZ)-induced diabetic rats. Nine weeks after STZ treatment, the mean cross-sectional area for retrogradely labeled (Fluoro-Gold) bladder neurons in the major pelvic ganglion (MPG) was greater in diabetics (364 microns 2) than controls (300 microns 2). The number of labeled neurons was similar in these groups. In contrast, mean cross-sectional areas of bladder afferent neurons labeled with WGA-HRP in the L6 and S1 dorsal root ganglia (DRG) were smaller (393 microns 2) in diabetics than in normal rats (528 microns 2). In addition, very few DRG neurons were labeled in STZ-treated rats and transganglionic labeling of bladder afferent projections in the L6 and S1 spinal cord with WGA-HRP was sparse. Radioimmunoassay studies revealed that substance P was reduced by 70% in the MPG and by 40% in L6 DRG, yet this peptide was unchanged in the bladders of diabetic rats. The amounts of VIP in the MPG and DRG of diabetics and controls were similar, while VIP in the bladder was increased in diabetics. These observations indicate that both afferent and efferent neurons innervating the urinary bladder are altered in the STZ-induced diabetic rat. In addition, axonal transport in visceral afferent pathways may be disrupted.

Urinary bladder dysfunction in the BB/W diabetic rat: effect of ganglioside treatment on functional and structural alterations

Urinary bladder dysfunction in the diabetic BB/W rat is characterized by infrequent irregular contractions of high amplitude. Initially these occur in the absence of detectable neuroanatomical lesions of sensory afferent and parasympathetic fibers of the pelvic nerve, which constitute the micturition reflex arc. Structural lesions consisting of progressive axonal atrophy of myelinated and unmyelinated fibers become detectable only after 4 months of diabetes. In the current study we evaluated the effect of ganglioside treatment (10 mg./kg. body weight) for one month. This drug regimen was initiated at 4 months of diabetes, when functional bladder abnormalities were well established, whereas structural lesions were yet to appear. Animals examined 1 or 3 months after termination of the one-month treatment protocol showed sustained normalization of the characteristic functional abnormalities, accompanied by prevention of the neuroanatomical lesions of sensory afferent and parasympathetic efferent myelinated fibers in the pelvic nerve. These data suggest that ganglioside treatment may be beneficial in delaying the progression of diabetic autonomic neuropathy in this experimental animal model.

Rat: overview and innervation

Despite the development of molecular and cellular methods for examining physiological processes, the use of the whole animal model remains essential to advance knowledge regarding the integration and coordination of events associated with urinary tract function. The rat offers an inexpensive and versatile species to investigate bladder and urethral responses to drugs or pathology. Models for many disorders have been developed in rodents including diabetes, multiple sclerosis, spinal cord injury, Parkinson's disease, bladder outlet obstruction, pain, and aging. This review examines methodologies to evaluate lower urinary tract function and manipulations used to create pathological models in rodents.

Energy turnover and lactate dehydrogenase activity in detrusor smooth muscle from rats with streptozotocin-induced diabetes

Force generation and tissue glucose metabolism were measured in the urinary bladder smooth muscle from rats with streptozotocin-induced diabetes (7-8 wk duration). Bladder wet wt was almost 4-fold higher in the diabetic animals compared with the untreated controls. Morphological analysis showed that the growth was associated with hypertrophy of the smooth muscle component in the bladder wall. Force generation of isolated bladder strip preparations was measured in vitro at different ambient oxygen tensions. Activation of intramural nerves, with electrical field stimulation, induced contractions that were unaffected by reduction of oxygen tension down to PO2 100 mmHg for both control and diabetic muscle strips. At zero PO2 force was reduced by approximately 10-20%, in both groups. High-K+ solution induced 'tonic' contractions that were slightly more inhibited by lowering PO2. At intermediate PO2 (between 100 and 20 mmHg) the diabetic muscle gave slightly higher force. At zero PO2 no significant difference could be detected between strips from control and diabetic animals. Oxygen consumption and lactate production in the preparations were determined at a PO2 of 290 mmHg and related to the volume of smooth muscle. At zero PO2, lactate formation increased 3- to 4-fold. The metabolic tension cost was lower at zero PO2. No differences in basal and contraction related metabolic rates could be detected between the two groups under normoxic and anoxic conditions. The maximal activity of lactate dehydrogenase (LDH) determined in tissue samples was about 2-fold higher in the diabetic bladder muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of age and streptozotocin-induced diabetes on contents and effects of substance P and vasoactive intestinal polypeptide in the lower urinary tract of the rat

The urinary bladder and urethral content of substance P and vasoactive intestinal polypeptide and the in vitro effects of the peptides on the bladder were studied at 6 weeks and 6 months of streptozotocin-induced diabetes in the rat. The results were compared with those obtained in age-matched control animals. Both short-term and long-term streptozotocin treatment induced a clearcut increase in bladder weight. Bladder substance P content was increased in both groups of diabetic animals but substance P concentration was similar in control and diabetic animals. Vasoactive intestinal polypeptide content was slightly higher in diabetic animals than in controls but vasoactive intestinal polypeptide concentration was significantly lower in the bladders from both short-term and long-term diabetic animals. The bladder contractile response to substance P was similar in all groups of animals and vasoactive intestinal polypeptide was found to be devoid of contractile or relaxatory effects in the rat bladder. No change in urethral weight was seen with diabetes. There were no clear-cut changes in the urethral contents or concentrations of substance P and vasoactive intestinal polypeptide. The study also enabled comparisons between younger (3 months) and older (9 months) rats. This comparison showed a decrease in the concentrations and contents of substance P and vasoactive intestinal polypeptide between young and older rats. The changes were seen in both the bladder and the urethra and were similar in diabetic and normal animals.

Reduced urinary bladder afferent conduction velocities in streptozocin diabetic rats

Previous experiments in our laboratory have described the method used to measure the conduction velocity distribution of a selected group of fibers (Brain Res., 520 (1990) 83-89). We have applied this technique to the 2 month streptozotocin-diabetic rat. Glycosylated hemoglobin values measured at the time of death were 17.19 +/- 4.74% (diabetic, n = 8) and 4.07 +/- 0.74% (controls, n = 6). Diabetic bladders were thicker and heavier. The wet weights were 0.50 +/- 0.11 g (diabetic, n = 7) and 0.16 +/- 0.01 g (controls, n = 6). The conduction velocities of a total of 151 and 86 single afferent fibers were measured in the diabetic and control animals respectively. The conduction velocity distribution of the diabetics showed a shift towards slower speeds when compared to controls. The mean conduction velocities were 1.70 m/s for diabetics and 2.84 m/s for controls. The percent of units with conduction velocities greater than 2.5 m/s was 17.2 for diabetics and 36.0 for controls. This experiment demonstrates, for the first time, that diabetes causes a significant reduction of afferent conduction velocities in a functionally well-defined system.