Decrease of catecholamine and neuropeptide Y-like immunoreactivity in the glycerol-induced acute renal failure of rats

Endothelial dysfunction and increased responses to renal nerve stimulation in rat kidneys during rhabdomyolysis-induced acute renal failure: role of hydroxyl radical

Rhabdomyolysis is an important cause of acute renal failure (ARF) and renal vasoconstriction is the main mechanism in the pathogenesis of ARF. Lipid peroxidation due to hydroxyl radical (.OH) formation and redox cycling of myoglobin also have a role. We investigated the disturbance in renal vascular reactivity to reveal the mechanisms leading to ARF. Female Wistar rats (n = 7) were injected with glycerol (10 mL/kg, 50% in saline) intramuscularly to induce rhabdomyolysis, and then the kidneys were isolated and perfused. We investigated acetylcholine (ACh)-induced endothelium-dependent and papaverine (PAP)-induced endothelium-independent vasodilation responses and renal nerve stimulation (RNS)-induced vasoconstrictions. These were also investigated both in rats which received either .OH scavenger, dimethylthiourea (DMTU: 500 mg/kg before glycerol injection and 125 mg/kg 8 h after glycerol injection, n = 7), or myoglobin redox cycling inhibitor, acetaminophen (ApAP: 100 mg/kg 2 h before glycerol injection and 100 mg/kg each 4 h, and 22 h after glycerol injection, n = 7). ACh-induced responses in glycerol group were decreased (p < 0.001), but PAP-induced vasodilation did not change. RNS-induced vasoconstriction in all kidneys was greater (p < 0.001) in glycerol group. DMTU restored both endothelium-dependent vasodilation and RNS-induced vasoconstriction. ApAP had no effect on vascular responses. Both DMTU and ApAP exerted a partial protective effect in renal histology without restoring serum creatinine and blood urea nitrogen (BUN) levels or creatinine clearance. This study showed that endothelial dysfunction and increased vasoconstriction developed during rhabdomyolysis. .OH plays an important role in the development of these vascular responses. These findings suggest that decreased endothelium-dependent vasodilation and augmented renal sympathetic tonus contribute to the development of renal vasoconstriction during rhabdomyolysis-induced ARF.

Uremic toxins in acute kidney injury

Acute kidney injury (AKI) is a serious and frequent condition which may fully resolve but is associated with markedly increased mortality. Mortality in AKI is caused by nonrenal, distant organ failure. Renal recovery from AKI is often not achieved on account of new injuries in the repair phase. Uremic toxins may be the missing link between AKI and nonrenal organ failure, tubular and endothelial injury. Compared with chronic kidney disease (CKD), research of uremic toxins in AKI is in its infancy. This review presents the current knowledge on uremic toxins in AKI which is predominately derived from experimental studies. Most uremic toxins investigated have previously been identified in CKD. The review focuses on those uremic toxins with biologic effect on the respective nonrenal organs failing in AKI and on the renal tubule and the endothelium. These uremic toxins may insofar be specific mediators of pathophysiological processes in AKI.

Adjuvant bupivacaine scalp block facilitates stabilization of hemodynamics in patients undergoing craniotomy with general anesthesia: a preliminary report

STUDY OBJECTIVE

To evaluate the effect of 0.25% bupivacaine scalp block on alterations in hemodynamics and plasma catecholamine metabolites during general anesthesia in patients undergoing frontotemporal craniotomy.

DESIGN

Prospective, clinical study.

SETTING

Operating room of a university hospital.

PATIENTS

16 ASA physical status II and III patients who were scheduled for frontotemporal craniotomy.

INTERVENTIONS

Patients were prospectively randomized to receive a saline control (C group) or bupivacaine scalp block (SB group) as an adjuvant to general anesthesia using isoflurane in 50% N(2)O-O(2).

MEASUREMENTS

Routine monitoring of electrocardiogram, heart rate (HR), and mean arterial blood pressure (MAP) were recorded at two-minute intervals from the beginning of anesthesia until 10 minutes after incision, followed by 5-minute intervals throughout the remaining course of the surgery. By prospective design, increases in MAP or HR by 20% above the mean baseline values were treated with 2.5 mg/kg of thiopental combined with 2 mug/kg of fentanyl. Arterial blood was sampled at 5 minutes before and after skin incision and at the start of dural opening for measuring serum catecholamine metabolites by high-performance liquid chromatography.

MAIN RESULTS

Only two patients in the SB group needed additional anesthetics for stabilizing their hemodynamics during the course of anesthesia. In contrast, all C group patients required supplemental anesthesia for controlling the abrupt rise in hemodynamic parameters. In addition, absolute MAP and HR values were significantly higher in the C group than in the SB group during the surgical period between incision and dural opening. The differences in hemodynamics observed between the two groups were, however, not accompanied with a significant change in plasma catecholamine metabolites at each predetermined time interval measured.

CONCLUSIONS

Pretreatment with 0.25% bupivacaine scalp block appeared to be an effective adjuvant treatment for maintaining stable hemodynamics for patients undergoing craniotomy during general anesthesia especially at the time of skin incision and dural opening. This study design was unable to discern any correlation between elevation in hemodynamic parameters and a rise in serum catecholamine levels.

Effects of sympathetic nerves and angiotensin II on renal sodium and water handling in rats with common bile duct ligature

We tested the hypothesis that angiotensin II is likely to be mandatory for the neurogenic sodium and volume retention in cirrhotic rats with common bile duct ligature (BDL) following an acute volume load. To assess the neural control of volume homeostasis, 21 days after common BDL rats underwent volume expansion (0.9% NaCL; 10% body wt over 30 min) to decrease renal sympathetic nerve activity. Untreated animals, rats with renal denervation or pretreated with a nonhypotensive dose of an angiotensin II type 1 receptor antagonist were studied. The renal renin-angiotensin system was assessed by immunohistochemistry and RT-PCR. Rats with BDL excreted only 71 ± 4% of the administered volume load. In cirrhotic rats pretreated with an angiotensin II AT1inhibitor or after renal denervation, these values ranged significantly higher from 98 to 103% ( P < 0.05 for all comparisons). Renal sympathetic nerve activity decreases by volume expansion were impaired in BDL rats ( P < 0.05) but unaffected by angiotensin II receptor inhibition. In kidneys of BDL animals, renin mRNA was increased, and immunohistochemistry revealed increased staining for peritubular angiotensin II. Renal denervation in BDL animals reduced renin expression within 5 days to control levels. In conclusion, the impaired excretion of an acute volume load in rats with liver cirrhosis is due to effects of an increased renal sympathetic nerve activity that are likely to be dependent on intrarenal angiotensin II and renin. We speculate that similar changes may contribute to long-term volume retention in liver cirrhosis.

Plasma glucose-lowering effect of tramadol in streptozotocin-induced diabetic rats

The effect of tramadol on the plasma glucose level of streptozotocin (STZ)-induced diabetic rats was investigated. A dose-dependent lowering of plasma glucose was seen in the fasting STZ-induced diabetic rats 30 min after intravenous injection of tramadol. This effect of tramadol was abolished by pretreatment with naloxone or naloxonazine at doses sufficient to block opioid mu-receptors. However, response to tramadol was not changed in STZ-induced diabetic rats receiving p-chlorophenylalanine at a dose sufficient to deplete endogenous 5-hydroxytrptamine (5-HT). Therefore, mediation of 5-HT in this action of tramadol is ruled out. In isolated soleus muscle, tramadol enhanced the uptake of radioactive glucose in a concentration-dependent manner. The stimulatory effects of tramadol on glycogen synthesis were also seen in hepatocytes isolated from STZ-induced diabetic rats. The blockade of these actions by naloxone and naloxonazine indicated the mediation of opioid mu-receptors. The mRNA and protein levels of the subtype 4 form of glucose transporter in soleus muscle were increased after repeated treatments for 4 days with tramadol in STZ-induced diabetic rats. Moreover, similar repeated treatments with tramadol reversed the elevated mRNA and protein levels of phosphoenolpyruvate carboxykinase in the liver of STZ-induced diabetic rats. These results suggest that activation of opioid mu-receptors by tramadol can increase the utilization of glucose and/or decrease hepatic gluconeogenesis to lower plasma glucose in diabetic rats lacking insulin.

Changes in endogenous monoamines in aged rats

1. It has been documented that ageing may alter endogenous neurotransmitters. However, these results are controversial. Thus, in the present study, cerebral cortex and plasma from male Wistar rats aged 8 weeks and 6, 12 or 24 months were used to investigate the changes in monoamines using electrochemical detection. 2. A marked decrease in L-dihydroxyphenylalanine (L-DOPA) was observed in aged rats. Like the decrease in dopamine (DA), levels of 5-hydroxytryptamine (5-HT) and 5-hydroxyindolacetic acid (5-HIAA), the major metabolite of 5-HT, in aged rats were decreased in the cerebral cortex and plasma. Plasma levels of noradrenaline and levels of adrenaline in the cerebral cortex were also decreased in aged rats. Moreover, levels of 3,4-dihydroxyphenylacetic acid (DOPAC), a metabolite of DA, in the cerebral cortex and plasma were reduced by ageing. The level of homovanillic acid (HVA) in all samples was markedly increased with ageing. 3. The ratio of DOPAC/DA and 5-HIAA/5-HT, being closely linked with the activity of monoamine oxidase, was increased in the cerebral cortex and plasma with ageing. The ratio of HVA/DOPAC, an index of the activity of catechol-O-methyltransferase, was also higher in the cerebral cortex and plasma of aged rats. 4. These data suggest that ageing may alter endogenous monoamines in both the brain and peripheral tissues.

Stimulatory effect of trans-cinnamaldehyde on noradrenaline secretion in guinea-pig ileum myenteric nerve terminals

The effect of trans-cinnamaldehyde (CNMA) on the release of noradrenaline (NA) from nerve terminal was investigated using isolated ileal synaptosomes of guinea-pig. Release was determined as the amount of NA, quantified by h.p.l.c.-electrochemical detection, from samples incubated with CNMA minus that in parallel blanks treated with same volume of vehicle. CNMA stimulated the secretion of NA in a concentration-dependent manner from 5 microM to 50 microM, while the value of lactate dehydrogenase in the incubated medium was not influenced by CNMA. However, trans-cinnamic acid, cinnamoyl chloride and cinnamamide failed to produce similar effect. Specific action of CNMA can thus be considered. Guanethidine inhibited the release of NA by CNMA in a concentration- dependent manner. Saxitoxin attenuated the action of CNMA at concentrations sufficient to block sodium channels. The depolarizing effect of CNMA on the membrane potential was also illustrated by a concentration-dependent increase in the fluorescence of bisoxonol, a potential sensitive dye. The NA releasing action of CNMA was deleted by removal of calcium chloride from the bathing medium. This action of CNMA was also attenuated by Rp-cAMP at concentrations sufficient to inhibit the action of cyclic AMP. These findings suggest that CNMA can depolarize the membrane to result in a calcium-dependent and cyclic AMP-related release of NA from noradrenergic terminals.

The effect of stevioside on blood pressure and plasma catecholamines in spontaneously hypertensive rats

Stevioside is a sweet-tasting glycoside, composed of stevia, a diterpenic carboxylic alcohol with three glucose molecules, mainly used as a substitute for non-alcoholic sweetener. It has previously been shown to reduce blood pressure in studies in animals and human. The effect of intravenous stevioside on the blood pressure was studied in spontaneously hypertensive rats (SHR). The hypotensive effect on both systolic and diastolic blood pressure was dose-dependent for intravenous doses of 50, 100 and 200 mg/kg in conscious SHR. The maximum reductions in systolic and diastolic blood pressure were 31.4 +/- 4.2% and 40.8 +/- 5.6% (mean +/- SEM) respectively and the hypotensive effect lasted for more than 60 min with a dose of 200 mg/kg. Serum dopamine, norepinephrine and epinephrine levels were not changed significantly 60 min after intravenous injection of stevioside 100 mg/kg in anesthetized SHR. The present data show that stevioside given intravenously to conscious SHR was effective in blood pressure reduction and there was no change in serum catecholamines in anaesthetized animals with this natural compound.

An ex vivo evaluation of regulatory role of biogenic amines in rat seminal vesicle after pharmacological manipulation

We studied the neural regulation of seminal vesicles (SV) by determining the changes of intraluminal pressure of rat SV in response to an electric stimulation of the lesser splanchnic nerve (LSN). After pharmacological manipulation with neurotoxin, the contents of monoamines and their metabolites in SV were estimated. In rats receiving electric stimulation of the LSN, an increase of intraluminal pressure was obtained with a reduction of the serotonergic turnover rate in SV. An intraperitoneal injection of DSP-4 (100 mg/kg), the noradrenergic neurotoxin, into rats decreased the level of norepinephrine (NE) in SV significantly but did not influence this functional response. Also, the intraluminal pressure was lowered by an intrathecal injection of 6-OHDA (20 microg/rat) to denervate spinal monoaminergic nerves in rats although the contents of monoamines in SV were not changed. This indicates that noradrenergic neurotransmission appears unimportant in this regulation. The lowering of intraluminal pressure in rats by 6-OHDA is mainly related to an attenuation of dopaminergic neuroregulation from the decrease of turnover rate of DA. Otherwise, an intrathecal injection of 5,7-DHT (60 microg/rat) to abolish spinal serotonergic nerves did not influence the level of monoamines in SV but increased the intraluminal pressure indicating an involvement of inhibitory regulation from spinal serotonergic pathway. These results suggest that contraction by electric stimulation of the LSN in Wistar rat SV is mainly regulated by the dopaminergic nervous pathway and an inhibitory regulation of the serotonergic nervous pathway from spinal cord while the noradrenergic nervous system seems unimportant for this regulation.

Renal denervation prevents and reverses hyperinsulinemia-induced hypertension in rats

Experiments were performed to evaluate the role of the renal nerves in hyperinsulinemia-induced hypertension. Male Sprague-Dawley rats were made hyperinsulinemic by insulin infusion via osmotic minipumps implanted subcutaneously (3.0 mU/kg per minute for 6 weeks). Rats with vehicle infusion served as controls. Bilateral renal denervation was performed either at the beginning of or 4 weeks after insulin infusion. The systolic blood pressure was measured by the tail-cuff method twice a week. Food and water intake and urine flow were measured daily. The results showed that sustained insulin infusion significantly increased plasma insulin concentrations from 277.7+/-25.8 pmol/L to 609.9+/-22.2 and 696.7+/-23.0 pmol/L by the end of weeks 4 and 6, respectively (P<0.05). Systolic blood pressure was significantly increased from 135+/-3 to 157+/-3 and 159+/-2 mm Hg (P<0.05) at the corresponding time points. There was a significant increase in the plasma norepinephrine concentration after insulin infusion, whereas no significant changes in plasma triglyceride and glucose concentrations, water intake, urine flow, sodium excretion, sodium gain, and body weight gain were observed. Bilateral renal denervation depleted renal norepinephrine stores and prevented the development of hyperinsulinemia-induced hypertension. After hyperinsulinemia-induced hypertension had been fully established (from 134+/-2 to 157+/-2 mm Hg), bilateral renal denervation reversed the elevated systolic blood pressure to normotensive levels within 2 weeks. Transient denervated diuresis and natriuresis were observed. These results indicate that chronic hyperinsulinemia-induced hypertension requires the presence of intact renal nerves in rats.

The role of free radicals in the release of noradrenaline from myenteric nerve terminals of guinea-pig ileum

In an attempt to understand the role of free radicals in the regulation of sympathetic neurotransmission, the in vitro secretion of noradrenaline (NA) from synaptosomal preparations of guinea-pig ileum was investigated. Release of endogenous NA was quantified by an electrochemical detection (HPLC-ECD). In the presence of superoxide dismutase (SOD) and catalase at concentrations sufficient to scavenge the free radicals, secretion of NA was attenuated in samples with stimulation of 4-aminopyrine (4-AP) or not (spontaneous release). However, inducing superoxide radicals via the reaction of hypoxanthine with xanthine oxidase failed to modify the secretion of NA, both the 4-AP-stimulated release and the spontaneous secretion. Then, free radicals were induced in synaptosomes using hypoxia-normoxia exposure. Secretion of NA was markedly increased in samples receiving this treatment in a calcium-dependent way because it was attenuated by the removal of calcium chloride from bathing medium. An increase of SOD activity, both Mn-SOD and Cu, Zn-SOD, was also obtained by this exposure. Changes of SOD activities in response to free radicals produced by hypoxia-normoxia exposure in ileal synaptosomes can thus be considered. In conclusion, these results suggest that free radicals are formed to involve in the regulation of sympathetic neurotransmission via an increase of calcium influx to enhance the NA release in guinea-pig ileum.

Simulatory effect of porcine insulin on noradrenaline secretion in guinea-pig ileum myenteric nerve terminals

1. The effect of insulin on the release of noradrenaline (NA) from nerve terminals was investigated in isolated ileal synaptosomes of guinea-pig. Release was determined as the amount of NA, quantified by h.p.l.c.-electrochemical detection, from samples incubated with insulin minus that in parallel blanks treated with some volume of vehicle. 2. Porcine insulin stimulated the secretion of NA in a concentration-dependent manner from 0.01 i.u. ml-1, while the value of lactate dehydrogenase in the incubated medium was not influenced by insulin. 3. The presence of insulin receptors in this preparation was illustrated by immunoblotting with insulin receptor monoclonal antibodies. 4. The release of NA by insulin was reduced by guanethidine and bretylium and it was markedly lowered in the samples obtained from guinea-pigs that had received an intraperitoneal injection of DSP-4, the noradrenergic neurotoxin. 5. Tetrodotoxin attenuated the action of insulin at concentrations sufficient to block sodium channels. The depolarizing effect of insulin on the membrane potential was also illustrated by a concentration-dependent increase in the fluorescence of bisoxonol, a potential-sensitive dye. 6. The action of insulin was attenuated by removal of calcium chloride from the bathing medium. The induction of calcium ion influx by insulin into the synaptosomes is supported by the inhibitory effects of the calcium channel blockers omega-conotoxin GVIA (for the N-type channels) and nifedipine (for the L-type channels). 7. These findings suggest that insulin can stimulate NA release from noradrenergic terminals via activation of calcium influx.

Isolation of synaptosomes from the rat urinary bladder

Synaptosomes are nerve-end particles (NEP) isolated by using the technique of differential centrifugation. The synaptosome offers a good model for biochemical and pharmacological studies of the nerve endings. No report has been made on synaptosome isolation from the urinary bladder. The purpose of our work was to develop the use of synaptosome in the research of neurophysiology and neuropharmacology of the urinary bladder. Synaptosome-rich fraction was prepared from tissue homogenate of male Wistar rat urinary bladder by differential centrifugation (1000, 17,000 and 100,000 g) with discontinuous sucrose gradient. Electron microscopy showed synaptosomes as thin-walled bags containing a large number of synaptic vesicles. Two types of synaptosomes were easily discerned: those containing small agranular vesicles, and those containing dense-cored vesicles. The acetylcholine, norepinephrine, epinephrine and dopamine contents in the preparation were measured by the method of high-performance liquid chromatography. The respective concentrations were 300.4 +/- 30.1, 962.8 +/- 58.5, 617.3 +/- 59.8 and 1354.8 +/- 144.2 pmol/mg synaptosomal protein. In conclusion, it has been demonstrated that synaptosome-rich fractions can be prepared from the rat urinary bladder. Thus it is possible to apply this methodology for the investigation of the neurobiology of urinary bladders.

Comparisons of neurotransmitter concentrations in the synaptosomal preparation of the normotensive and hypertensive rat urinary bladder

Synaptosome-rich fractions were prepared from tissue homogenate of the urinary bladder of the spontaneously hypertensive rat and normotensive Wistar-Kyoto rat 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 normotensive rats were 300.4 +/- 30.1, 962.8 +/- 58.5, 617.3 +/- 59.8, and 1354.8 +/- 144.2 pmol/mg synaptosomal protein. For the hypertensive rats, the acetylcholine concentration (203.8 +/- 23.0 pmol/mg protein) was significantly lower (P < 0.05), while the norepinephrine, epinephrine and dopamine concentrations (1459.0 +/- 180.3, 971.3 +/- 62.2, and 2161.0 +/- 243.4 pmol/mg protein, respectively) were significantly higher (P < 0.05 for all) than those of the normotensive rats. In conclusion, it has been demonstrated that the vesicle-bound catecholamines in the synaptosome-rich fraction of the urinary bladder were significantly increased in hypertensive rats. On the contrary, the synaptosomal acetylcholine concentration was significantly decreased. These findings are suggestive of increased sympathetic innervation and decreased parasympathetic innervation in the urinary bladder of the spontaneously hypertensive rat.

The norepinephrine tissue concentration and neuropeptide Y immunoreactivity in genitourinary organs of the spontaneously hypertensive rat

Tissue concentration of norepinephrine and neuropeptide-Y immunoreactivity (NPY-IR) were measured in the urinary bladder, urethra, prostate and corpus cavernosum of the spontaneously hypertensive rat, as well as the normotensive Wistar-Kyoto rat. The results showed significantly increased tissue norepinephrine concentrations in the urinary bladder, urethra and prostate of the spontaneously hypertensive rat when compared to those of the normotensive rat (hypertensive, n = 18: 18.3 +/- 2.1, 14.9 +/- 1.7, 22.6 +/- 2.3 vs. normotensive, n = 18: 11.2 +/- 1.9, 10.4 +/- 1.3, 16.7 +/- 2.4 nmol/g tissue, respectively, P < 0.05 in each case). No difference was noted in the cavernosal tissue (hypertensive, n = 18: 11.3 +/- 1.6 vs. normotensive, n = 18: 10.1 +/- 1.8 nmol/g tissue, P > 0.01). Correspondingly, tissue NPY-IR was significantly increased in the bladder, urethra and prostate tissue of the spontaneously hypertensive rat (hypertensive, n = 18: 39.7 +/- 5.6, 25.3 +/- 3.4, 31.5 +/- 2.8 vs. normotensive, n = 18: 27.4 +/- 3.1, 18.6 +/- 2.7, 24.2 +/- 3.2 pmol/g tissue, respectively, P < 0.05 in each case). Again, no significant difference was observed in the cavernosal tissue (hypertensive, n = 18: 15.9 +/- 2.2 vs. normotensive, n = 18: 14.8 +/- 2.6 pmol/g tissue, P > 0.01). It is therefore concluded that increased tissue concentration of norepinephrine and NPY-IR were present in the urinary bladder, urethra and prostate of the spontaneously hypertensive rat. The significance of such biochemical findings needs further investigation but may suggest increased sympathetic innervation or activity. On the contrary, no corresponding changes were observed in the corpus cavernosum of the hypertensive rat.

Antihypertensive action of geraniin in rats

The effects of geraniin, one of the ellagitannins purified from the leaves of Sapium sebiferum, on blood pressure were investigated in the spontaneously hypertensive rat (SHR). A single intravenous bolus injection of geraniin into anaesthetized SHRs lowered the arterial mean blood pressure in a dose-dependent manner without affecting the heart rate. A similar action was also observed in the normotensive (WKY) rat that received this compound at a higher dose. Geraniin did not modify the baroflex sensitivity in the phenylephrine-challenged SHR. This tannin reduced the plasma noradrenaline in a dose-dependent fashion which was not influenced by adrenalectomy. Failure of the antagonists, idazoxan and yohimbine for alpha 2-adrenoceptors as well as haloperidol and domperidone for dopamine receptors, to reverse the antihypertensive actions of geraniin ruled out the possible mediation of these receptors. Moreover, geraniin attenuated the pressor responses to exogenous noradrenaline and Bay K 8644 to a similar degree, indicating the direct effect of this compound on vascular activity in rats. These results suggest that geraniin possesses the ability to lower systemic blood pressure through the reduction of noradrenaline release or by direct vasorelaxation.

Increase of plasma neuropeptide Y-like immunoreactivity following chronic hypoxia in the rat

In an attempt to understand the changes of circulating neuropeptide Y (NPY) during hypoxia, the plasma level of NPY was investigated by radioimmunoassay. Exposure of rats to hypobaric hypoxia at an altitude of 18,000 ft for 4 weeks causes an increase of pulmonary pressure and an elevation of plasma NPY-like immunoreactivity (NPY-LI). However, the systemic blood pressure was not elevated by this chronic hypoxia. Also, plasma noradrenaline (NA) estimated by chromatographic analysis (HPLC-ECD) was not markedly raised. Failure of bretylium and guanethidine, sympathetic neuron blockers, in reducing the plasma NPY-LI level of these rats ruled out the participation of adrenergic nervous terminals. Adrenal medulla seems responsible for this elevation of plasma NPY-LI because this magnitude disappeared in adrenalectomized rats. These data suggest that chronic hypoxia induced an elevation of circulating NPY from the adrenal gland of rats.