Sex-specific regional brain bilirubin content in hyperbilirubinemic Gunn rat pups

BACKGROUND: The hyperbilirubinemic j/j Gunn rat is frequently used to study the effects of neonatal hyperbilirubinemia on the developing central nervous system (CNS). Despite evidence that the cerebellar region and males are predisposed to bilirubin-induced brain injury in this animal model, there are limited regional and no sex-specific brain bilirubin content data. OBJECTIVE/METHODS: To characterize and contrast the regional (cortex, brainstem, cerebellum) and sex-specific CNS bilirubin contents of hyperbilirubinemic j/j Gunn rat pups and their age-matched (15-19 days) nonjaundiced J/j counterparts. Pups were injected 24 h prior to sacrifice with sulfadimethoxine (200 mg/kg i.p.) to enhance the CNS bilirubin content. RESULTS: The CNS bilirubin contents in each region and total serum bilirubin levels were significantly greater in jaundiced j/j pups versus nonjaundiced J/j pups. Within the sulfadimethoxine-treated male j/j cohort, the mean brain bilirubin content was highest in the cerebellum (18.9 +/- 7.8 microg/g), intermediate in the brainstem (10.7 +/- 8.0 microg/g), and lowest in the cortex (4.7 +/- 3.0 microg/g) (F = 11.31, p < 0.001 by ANOVA), and the cerebellar bilirubin level was significantly higher than in the littermate-matched sulfadimthoxine-treated j/j female pups (p < 0.02). The serum albumin levels were not different between j/j male and j/j female pups. CONCLUSIONS: We conclude that the brain bilirubin content of hyperbilirubinemic j/j Gunn rat pups is greater than in nonjaundiced J/j pups and varies as a function of CNS region and sex. We speculate that the higher cerebellar bilirubin content may preferentially predispose male j/j Gunn rat pups to bilirubin-induced neurotoxicity.     

Auditory brainstem response and unbound bilirubin in jaundiced (jj) Gunn rat pups

The role of plasma bilirubin-albumin binding in the pathogenesis of kernicterus in human newborns is controversial. Kernicterus in the jaundiced (jj) Gunn rat pup, an animal model for kernicterus, prolongs interwave intervals and decreases wave amplitude in the auditory brainstem response (ABR). Plasma total bilirubin concentration (TBC), albumin concentration, and unbound bilirubin concentration (UBC), a measure of bilirubin-albumin binding, were measured in 16-day-old jj Gunn rat pups (n = 21) and compared with ABR wave latencies, interwave intervals, and wave amplitudes by linear correlation. The UBC, but not the TBC or TBC/albumin ratio, correlated positively and significantly with ABR I-II and I-III interwave intervals (r = 0.55, p = 0.009, and r = 0.60, p = 0.004, respectively). The UBC, but not the TBC or TBC/albumin ratio, predicts bilirubin toxicity, as measured by bilirubin-induced ABR changes in jj Gunn rat pups.     

Effect of irradiation on the erythrocyte membranes of homozygous Gunn rat sucklings

Erythrocyte membranes were isolated from irradiated Gunn's strain of jaundiced rat sucklings, and photodynamic action of bilirubin in vivo was investigated using sodium dodecyl sulfate-polyacrylamide-gel electrophoresis. The effectiveness of irradiation was verified in terms of decrease of plasma bilirubin concentrations and cerebellar bilirubin contents, and also by recovery from the cellbellar hypoplasia, a characteristic feature of the homozygotes (j/j). The cross-linking of erythrocyte membrane proteins by photodynamic action of bilirubin was demonstrated in vitro in rat erythrocytes as reported for human erythrocytes by Girotti (Biochemistry 14: 3377, 1975). The phenomenon, however, was not observed in vivo. Instead, a protein band with a mol. wt. of 32,000 was increased by the irradiation both in the homozygous (j/j) and heterozygous (j/+) Gunn rats.     

A new animal model of hemolytic hyperbilirubinemia-induced bilirubin encephalopathy (kernicterus)

Neonatal hyperbilirubinemia can cause bilirubin encephalopathy (kernicterus). Spontaneously jaundiced (jj) Gunn rats treated with sulfonamide (sulfa) to displace bilirubin from serum albumin, develop bilirubin encephalopathy and abnormal brainstem auditory evoked potentials (BAEPs) comparable with human newborns. We hypothesized phenylhydrazine (PHZ)-induced hemolysis would significantly elevate total plasma bilirubin (TB) in jj Gunn rat pups and produce BAEP abnormalities similar to those observed after sulfa. PHZ 0, 25, 50, or 75 mg/kg was administered intraperitonealy to 15-d-old jjs. An initial TB was recorded in each animal, and a second recorded 1-4 d postinjection to generate a dose-response curve. After PHZ 75 mg/kg, TB peaked at about 30 mg/dL at 48-72 h. A second group of jjs injected with PHZ (0, 25, 50, or 75 mg/kg) and nonjaundiced controls given PHZ 75 mg/kg had HCT and TB at baseline, and HCT, TB, and BAEPs recorded at 48 h. BAEP wave II and III amplitudes decreased, and I-II and I-III interwave intervals increased indicating abnormal central (brainstem) auditory function. PHZ-induced hemolysis in jaundiced Gunn rat pups produces sufficiently elevated TB levels to produce bilirubin encephalopathy. This new model may be a more clinically relevant experimental model of kernicterus- and bilirubin-induced neurologic disorders.     

The effect of zinc salts on serum bilirubin levels in hyperbilirubinemic rats

OBJECTIVES: Intestinal metabolism of bilirubin is implicated in the pathogenesis of neonatal jaundice and Crigler-Najjar syndrome. In the present study the authors investigated the effect of oral administration of zinc salts on serum bilirubin levels in hyperbilirubinemic rats. METHODS: Bilirubin-binding activities of zinc sulfate and water-insoluble zinc methacrylate were determined in vitro. Congenitally hyperbilirubinemic Gunn rats and artificially hyperbilirubinemic Wistar rats were used in in vivo studies. Animals were fed a normal diet for 1 week and then a treatment diet of either zinc sulfate or zinc methacrylate for additional 2 weeks. Serum and fecal bile pigments were determined at the end of each phase. Biliary bilirubin secretion rates were determined in hyperbilirubinemic Wistar rats fed zinc methacrylate. RESULTS: Substantial bilirubin-binding activities of zinc salts were demonstrated in in vitro experiments. Treatment with oral zinc salts significantly decreased serum bilirubin levels in Gunn rats (166 +/- 53 versus 123 +/- 38 and 206 +/- 34 versus 131 +/- 31 micromol/L, P < 0.05 for zinc methacrylate and zinc sulfate, respectively). A similar effect of zinc methacrylate was also observed in hyperbilirubinemic Wistar rats (102 +/- 10 versus 14 +/- 4 micromol/L, P < 0.0001). In accord, biliary bilirubin secretion decreased significantly in these animals (45 +/- 11 versus 28 +/- 4 nmol/h 100g body weight, P < 0.02). In contrast to zinc sulfate, treatment with zinc methacrylate did not lead to the elevation of serum zinc levels. CONCLUSIONS: Oral administration of zinc salts efficiently decreased serum bilirubin levels in hyperbilirubinemic rats, presumably as a result of inhibition of enterohepatic circulation of bilirubin. This approach might be useful in the treatment of severe unconjugated hyperbilirubinemias.     

Danger of bucolome in infants with hyperbilirubinaemia. Experimental evidence.

Effects of bucolome on congenitally jaundiced Gunn rats were examined. Plasma total bilirubin level fell immediately after a single injection of bucolome and the lowered level persisted for more than 6 hours. Plasma unbound-bilirubin level and cerebellar bilirubin content increased simultaneously with the drop in total plasma bilirubin level. Kernicterus was observed in the brains of the treated rats 6 hours after the treatment. LD50 of the drug in jaundiced rats was about 37 mg/kg, about one-tenth of the value in nonjaundiced rats. It is suggested that bucolome displaces bilirubin from albumin, transferring bilirubin from blood into tissues including the brain, and resulting in kernicterus. The use of bucolome in infants with hyperbilirubinaemia is inadvisable.     

Effect of Sulfisoxazole on Bilirubin-Albumin Binding in Gunn Rats

Hyperbilirubinemic Gunn rats were used to study sulfisoxazole-mediated displacement of bilirubin from albumin. Bilirubin not bound to albumin or unbound bilirubin, which can enter the brain and cause damage, was measured by the automated peroxidase micromethod using the UB-Analyzer. When sulfisoxazole was added to the rat serum in vitro, it showed measurable displacing competition with bilirubin for the binding sites on albumin. The bilirubin titration curves of hyperbilirubinemic sera, after injection of sulfisoxazole, showed a shift to the left indicating that the drug effectively lowered the capacity of serum albumin to bind to bilirubin. The bilirubin binding affinity of the first binding site on the albumin decreased with the administration of 25 mg/kg or more of sulfixazole. The serum concentration of both total bilirubin and unbound bilirubin decreased after the injection of sulfisoxazole suggesting their diffusion into extravascular compartments.     

Diagnosis and management of Crigler-Najjar syndrome

Crigler-Najjar syndrome (CNS) results from a mutation in one of the five exons of the gene coding for the enzyme bilirubin-UDP-glucuronosyltransferase by exon 1*1 and exons 2-5 of the UDP-glucuronosyltransferase 1 locus, the bilirubin glucuronidating isoform of UDP-glucuronosyltransferase. CNS type 2 is caused by a single base pair mutation leading to a decreased but not totally absent enzyme activity. In these patients the enzyme remains responsive to phenobarbital induction therapy and their bile contains low amounts of bilirubin mono- and diglucuronides. In CNS type 1 the enzyme activity is completely absent. CNS type 1 patients do not respond to phenobarbital and their bile does not contain more than traces of bilirubin conjugates. In 1997 we reported a World Registry on the treatment of patients with CNS type 1. Data were collected on 57 patients, of whom 21 (37%) had been transplanted at the time of data collection. Some 15 patients (26%) had brain damage, in 7 of whom the brain damage was mild and they received a liver transplant. Patients with brain damage at transplantation were significantly older than those without brain damage (14.3 vs 5.9 years). Before transplantation the serum bilirubin level of CNS type 1 patients should be kept below 350 7mol/l with daily phototherapy. Oral calcium supplementation makes phototherapy more efficient. Gene therapy has been performed successfully in the Gunn rat, an animal model for this disease. Liver cell transplantation has recently been done in a child with CNS type 1.     

Transfer of bilirubin covalently bound to 125I-albumin from blood to brain in the Gunn rat newborn.

Transfer of bilirubin covalently bound to albumin (Alb.B) from blood into brain was examined in Gunn rats at postnatal day 3, 7, 14, 28 or 70. The ratio of the 125I-Alb.B concentration in the brain to that in the plasma 2 h after the injection (RAB) was used as a criterion for Alb.B transfer. RAB in brain decreased with age until day 28. Significant correlations were indicated between 125I-Alb.B plasma levels and those in the brain at days 7 and 14, but not at day 28. These results suggested that 125I-Alb.B could transfer from the blood to the brain until day 14. Comparison of the relative amount of radioactivity accumulated in the brain by a 125I-Alb.B injection with that of 125I-albumin alone revealed higher radioactivity in the former than the latter only at day 14, suggesting a transient appearance of particular cellular elements with high affinity to bilirubin in the developmental stage of the brain.     

A difference in mortality between two strains of jaundiced rats

Homozygous Gunn rats lack bilirubin glucuronyltransferase, become jaundiced, and often develop kernicterus, thus providing a model for neonatal hyperbilirubinemia. Two new, inbred rat strains that carry the Gunn mutation are described. These were developed by breeding the mutant Gunn gene (j) into the RHA/N and ACI/N strains, producing the new lines, which were designated RHA/N-j and ACI/N-j. Liver assay confirmed the absence of transferase activity in jaundiced rats from both of the new strains, but marked differences in mortality between the strains were observed. The mortality of jaundiced RHA/N-j rats through 8 weeks was the same as that of their nonjaundiced littermates (20%). In contrast, mortality of jaundiced ACI/N-j rats was distinctly greater than that of their nonjaundiced littermates (81% vs 34%, P less than .001). Signs of kernicterus such as ataxia were much more frequent in jaundiced ACI/N-j rats than in jaundiced RHA/N-j rats (73% vs 11%, P less than .001). Both strains had comparable albumin concentrations through 8 weeks of age. Serum bilirubin concentrations were also comparable, except for a small but significant difference at 20 days of age (ACI/N-j = 294 mumols/L, RHA/N-j = 248 mumols/L, P less than .01). Similarly, the bilirubin-to-albumin ratios were comparable except for a significantly higher ratio at 20 days of age in the ACI/N-j rats (ACI/N-j = 0.70, RHA/N-j = 0.51, P less than .01). Thus, the RHA/N-j strain is unusual in that the jaundiced animals remain healthy. Conversely, the ACI/N-j animals demonstrate a high incidence of kernicterus with mortality.(ABSTRACT TRUNCATED AT 250 WORDS)     

Autoradiography with 14C-bilirubin in pregnant normal Wistar rats and Gunn rats with and without phenobarbital or albumin administration

Pregnant normal Wistar rats and Gunn rats were given 25 Ci (1 mg) ¹⁴C-bilirubin intravenously. They were killed at different intervals. Whole-body autoradiography was used to study the different pathways of bilirubin in normal rats and in Gunn rats. Numerous spots of intense blackening were seen on the autoradiographs in the area of the liver of normal rats, indicating biliary excretion of the administered isotope. In the autoradiographic picture of the Gunn rat liver more diffuse blackening was present. In the normal rat the bowels contained radioactive material shortly after the injection, whereas in Gunn rats no radioactivity was demonstrable within the lumen of the bowels; the area over the bowel wall showed intense staining suggesting some mucosal excretion of bilirubin, however. The isotope content of the renal cortex was somewhat higher than that of the medulla in all animals. In addition, the papillae of the Gunn rat kidney contained a very high level of radioactivity; crystallization of bilirubin takes place in this area. Usually there was no radioactivity in the brain or spinal cord outside the vessels. One Gunn rat with an apneic spell immediately after the injection of bilirubin has isotope deposits throughout the brain. The fetuses of normal and Gunn rats showed less radioactivity than the mother animals. The lumen of the fetal bowels was always free of radioactivity even in fetuses of normal Wistar rat mothers with large amounts of the isotope within the gut. With the aid of the stripping-film technique it was possible to demonstrate that some isotope was localized within the liver cell as soon as 30 sec after the injection. In normal Wistar rats only an intense blackening was visible over the bile capillaries and intrahepatic bile ducts in later stages of the experiments.If albumin was given in addition to ¹⁴C-bilirubin the same autoradiographic pattern was obtained. Phenobarbital pretreatment caused no autoradiographic changes.Dedicated to Professor Dr. G. Joppich, Göttingen, on the occasion of his 70th birthday.     

Stage-Specific Relationship between Plasma Total and Cerebellar Bilirubin Levels during Early Postnatal Period in Jaundiced Gunn Rats

Abstract Relationships between plasma total or unbound bilirubin level and cerebellar bilirubin level were examined during the first 14 days after birth in homozygous Gunn rats with hyperbilirubinemia. Correlation coefficients between plasma total and cerebellar bilirubin levels were 0.63, 0.74, 0.48 and 0.60 at days 3, 7, 9 and 11, respectively, and were all significant, whereas the coefficient at day 14 (0.10) was not significant. The correlation coefficients between plasma unbound and cerebellar bilirubin levels were 0.40, 0.09, and 0.12 at days 7, 11 and 14, respectively, and were not significant. Thus, the cerebellar bilirubin level is suggested to depend on the plasma total bilirubin level from day 3 to 11.     

Pharmacological and biological effects of tin-protoporphyrin on neonatal hyperbilirubinemic Gunn rats

Our study was undertaken to examine the pharmacological and biological effects of tin-protoporphyrin, a competitive inhibitor of heme oxygenase, on 5- or 6-day-old homozygous (j/j) Gunn rats with hereditary unconjugated hyperbilirubinemia. When j/j neonates were injected subcutaneously with 20 mumol of tin-protoporphyrin/kg of body weight, hepatic heme oxygenase activity decreased to 30% of the initial level 2 h after administration and remained low during the next 46 h. However, the reduction of serum bilirubin was more rapid and transient, reaching the minimum value (40% of the initial level) at 1 h and increasing thereafter at a rate almost comparable to that in nontreated j/j rats. The mortality rate of j/j rats was strikingly reduced by the administration of 1 to 100 mumol of tin-protoporphyrin/kg; the most effective dose was 5 mumol/kg (8% compared with 80% in non-treated j/j rats). However, the protective effect of tin-protoporphyrin on bilirubin cerebellopathy (cerebellar hypoplasia) was less marked than expected. Possible implications of our results are discussed.     

Effects of sulfadimethoxine on tissue distribution of (14C)bilirubin in the newborn and adult hyperbilirubinemic Gunn rate.

Sulfadimethoxine significantly reduced plasma bilirubin levels and altered the tissue bilirubin distribution in both the newborn and the adult Gunn rat. The majority of the unbound bilirubin appeared to distribute perferentially to the intestine and liver in the newborn, whereas in the adult the unbound bilirubin was taken up primarily by the liver. The bilirubin content of brain tissue from both age groups was significantly higher after sulfadimethoxine treatment.     

Transcutaneous bilirubinometry: a noninvasive tool for studying newborn jaundiced rats before and after exposure to light

The homozygous Gunn rat is the most frequently used animal model for the study of neonatal jaundice. We evaluated the applicability of noninvasive transcutaneous bilirubin (TcB) measurements as an index of serum total bilirubin (STB) levels in neonatal rats by comparison to invasive STB measurements. TcB measurements were made during the first 96 h of life with the Model 101 Minolta/Air-Shields Jaundice Meter (JM) and SpectRx BiliCheck System (BC). Measurements with both devices displayed parallel TcB profiles, rapidly rising within 24 h, increasing during the next 6 h, then leveling off after 30 h. Linear regressions for the JM (n = 60) were as follows: STB (mg/dL) = 0.79 (JM) - 0.01 (units, r = 0.95, head); STB (mg/dL) = 0.82 (JM) + 1.51 (units, r = 0.95, upper back); and STB (mg/dL) = 0.74 (JM) + 1.60 (units, r = 0.91, lower back). Mean bias +/- imprecision were as follows: -0.02 +/- 3.99 mg/dL, -0.01 +/- 3.90, and 0.01 +/- 4.28 at the head, upper back, and lower back, respectively. For the BC, only lower back measurements were taken, and the regression was as follows: STB (mg/dL) = 0.77 (BC) + 1.65 mg/dL, (r = 0.93, n = 29) with a mean bias +/- imprecision of -1.08 +/- 3.08 mg/dL. When pups were exposed to light, correlations remained strong but intercepts increased. These results demonstrate that noninvasive TcB measurements correlate highly with STB in the Gunn rat during the first 96 h of life and after exposure to light. We conclude that JM measurements at the head and BC at the lower back reflect STB most reliably and consistently. Thus, in addition to being a useful tool for evaluating jaundice in human neonates, TcB methodology can be used successfully for the noninvasive monitoring of jaundice in neonatal Gunn rats pre- and postlight exposure.     

Blood-brain barrier permeability to bilirubin in the rat studied using intracarotid bolus injection and in situ brain perfusion techniques

It has generally been assumed that free unconjugated bilirubin gains access to the brain because of its lipid solubility. However, no measurements of the blood-brain barrier permeability to free bilirubin exist. The aim of these experiments was to determine the blood-brain barrier permeability in the rat to free bilirubin using single-pass (Oldendorf) and in situ perfusion (Takasato) techniques. Studies were performed on adult rats under sodium pentobarbitone anesthesia. [3H]bilirubin IX-alpha-ZZ (sp act 6.2 Ci/mmol) was synthesized by reduction of biliverdin with sodium boro-[3H]hydride. Blood-brain barrier permeability to albumin-bound and free bilirubin was determined using injectates/perfusates containing a molar excess of human serum albumin with or without the addition of the displacing agent sulphadimethoxine. For free bilirubin, the brain uptake index was 28.5 +/- 9.3 (mean +/- SD, n = 18), and the permeability surface area product was 54.84 +/- 36.38 x 10(-4) mL/s/g (mean +/- SD, n = 13). These results demonstrate that the behavior of free bilirubin in vivo in relation to the cerebral microvasculature corresponds to that of a "lipid soluble" molecule.     

Somatosensory and brainstem auditory evoked potentials in the Gunn rat model of acute bilirubin neurotoxicity

Brainstem auditory evoked potentials (BAEPs) are a sensitive indicator of bilirubin neurotoxicity. Somatosensory evoked potentials (SEPs) have been proposed as another measure of toxicity, though the lemniscal pathways that generate the SEP are not involved in kernicterus. In 16 to 17-d-old jaundiced (jj) Gunn rats, serial BAEPs and SEPs were obtained up to 8 h after acute bilirubin toxicity. jjs were injected with 150 mg/kg sulfadimethoxine to displace bilirubin into brain tissue (n = 8); littermate controls were jjs given saline (n = 4) and nonjaundiced given sulfadimethoxine or saline (n = 7). After anesthesia, BAEP and SEP recordings were obtained at baseline and serially after injection. SEPs to median nerve stimulation were recorded from surface electrodes over the brachial plexus (Erb's) and contralateral parietal cortex, and subtracted to obtain central conduction time (CCT). There were no statistically significant different baseline values between groups. Baseline BAEP I, I-II, and I-III were 1.22 +/- 0.13, 1.11 +/- 0.12, and 2.10 +/- 0.15 ms, and SEP Erb's and CCT were 1.48 +/- 0.20 and 5.59 +/- 0.50 ms, respectively (n = 19). At 6.8 +/- 1.5 h after injection BAEP I, I-II, and I-III increased 0.10 +/- 0.08, 0.18 +/- 0.17, and 0.56 +/- 0.33 ms over baseline, respectively (p = 0.005, 0.01, and 0.001, respectively, paired, 1-tailed t-tests), in experimental but not control groups. SEP Erb's decreased slightly, -0.06 +/- 0.04 ms in experimental and -0.08 +/- 0.08 ms in control groups, while CCT did not change significantly. BAEPs were completely abolished in two jjs with no SEP changes. When injection of sulfonamide induced significant peripheral and central BAEP abnormalities in jaundiced rats, no SEP abnormalities occurred. SEPs assess proprioception but not other somatosensory function or sensory integration. The results demonstrate the selectivity of acute bilirubin toxicity for the auditory nervous system.     

长程服用苯巴比妥、氯硝安定、丙戊酸和托吡酯对未成熟脑发育影响的实验研究

目的探讨治疗血浓度下常用抗癫痫药（AEDs）对未成熟脑损伤的可能性。方法160只健康sD大鼠,幼鼠与成年鼠各80只。以AEDs血浓度达到临床治疗稳态血浓度为实验剂量,设立健康7日龄幼鼠及2月龄成年SD大鼠氯硝安定（CZP）、苯巴比妥（PB）、丙戊酸钠（VPA）、托吡酯（TPM）给药组及正常对照组。每一给药组又分为2周短程及5周长程给药组,每组8只。停药当天称取体重及脑重,尼氏染色及电镜观察脑组织病理改变,ELISA法测定血清神经元特异性烯醇化酶（NSE）含量,免疫组化检测Bcl-2、Bax蛋白表达,原位末端标记法（TUNEL）检测凋亡细胞。结果（1）短程PB给药幼鼠血清NSE浓度[（8．84±2．10）nmol／L]较正常对照[（6．27±1．27）nmol／L]高,差异有统计学意义（P〈0．01）;（2）长程CZP及PB组幼鼠脑重较对照明显减轻,额叶皮层神经细胞减少,神经元超微结构明显异常,血清NSE浓度[分别为（8．15±1．67）nmol／L及（8．07±1．27）nmol／L]较对照[（6．02±1．20）nmol／L]高,差异有统计学意义（P〈0．01）,Bax蛋白表达强于正常对照组（P〈0．01）,TUNEL染色阳性细胞较对照组多。结论治疗血浓度下4种AEDs中,PB、CZP可引起发育中脑组织明显而持久的组织学损伤及神经元坏死与过度凋亡。     

Effect of postnatal anoxia on bilirubin levels in rat brain

The effects of a period of anoxia 18-24 h after birth on bilirubin levels in rat brain were investigated during anoxia, recovery, and development. Postnatal anoxia induces a significant, temporary increase (up to 200% with respect to control values) in newborn rat brain bilirubin levels during anoxia and short-term recovery. Pretreatment of the newborn rats with a single dose of the drug sulfixosazole markedly enhances bilirubin accumulation in the brain of the anoxic rats. A second rise in brain bilirubin concentration is detected in a group of the newborn rats 3-6 days after oxygen deprivation. Autoradiographic localization of radiolabeled bilirubin following in vivo experiments suggests that this substance is preferentially accumulated in some areas of the newborn rat brain as a consequence of postnatal anoxia, and indicates, together with the effect of sulfixosazole, that as a result of anoxia, a displacement of unbound bilirubin from blood to the nervous tissue occurs. Our results confirm the importance of anoxia as a risk factor for the development of bilirubin-induced encephalopathy. The possible relevance of intracerebral hemorrhages caused by perinatal asphyxia producing delayed bilirubin accumulation in the newborn rat brain is suggested.     

The in vivo effect of bilirubin and sulfisoxazole on cerebral oxygen, glucose, and lactate metabolism in newborn piglets

Bilirubin inhibits in vitro oxidative phosphorylation and glycolysis. This study investigated the in vivo effect of bilirubin on cerebral oxygen, glucose, and lactate uptake in newborn piglets. Seventeen 2- to 4-day-old piglets were divided into three groups and examined as follows: group 1 = control (C); group 2 = control with sulfisoxazole; and group 3 = experimental, given bilirubin with sulfisoxazole. In the experimental group, bilirubin was infused for 4 h. The cerebral bilirubin content in the bilirubin-infused group was 11.0 +/- 1.4 nmol/g of cerebral cortex (mean +/- SEM), consistent with levels found in infants with kernicterus. However, this level of brain bilirubin had no major, acute effects on cerebral uptake of oxygen, glucose, or lactate despite producing lethargy and ataxia which were consistent with bilirubin intoxication. This suggests that mitochondrial changes may not be involved in vivo in acute bilirubin encephalopathy.