Plasma phenylalanine: Tyrosine ratios during high-dose methotrexate-citrovorum “rescue”

We have measured phenylalanine and tyrosine in the plasma of patients with osteogenic sarcoma undergoing chemotherapy with high-dose methotrexate (HDMTX) citrovorum factor rescue (CFR). During 14 treatments in six different patients, the phenylalanine to tyrosine ratio (PHE/TYR) at 21 to 38 hours was elevated over pretreatment levels. The observed increase in plasma phenylalanine is attributed to inhibition by MTX of the phenylalanine hydroxylase system of the liver, which is not folate-dependent and thus is not corrected by administration of CF. A post-infusion increase in PHE/TYR of 571% after 22 hours in one patient and of 410% after 30 hours in another were associated with marked MTX toxicity. The greatest increase in PHE/TYR seen in a patient who did not experience toxicity was was 249% in 21 hours. Thus, in this group of patients, there appears to be a correlation between evidence of clinical MTX toxicity and the magnitude of the percentage increase in PHE/TYR in the plasma, which indicates inhibition of a liver enzyme and thus reflects the intracellular concentration of MTX.     

A simple method for detection of heterozygous carriers of the gene for classic phenylketonuria

Plasma phenylalanine (Phe) and tyrosine (Tyr) concentrations were measured by high-performance liquid chromatography in arteriolar blood obtained by finger prick from 78 normal volunteers and 36 heterozygote carriers of phenylketonuria (PKU). Subjects were tested at midday, 3 to 4 hours after their breakfast. Values for the micromolar ratio of Phe/Tyr and Phe2/Tyr for control subjects fell below 1.2 and 80, respectively; values for all carriers of PKU were higher for one or both ratios. This method should be applicable to widespread screening of the general population for carriers of the gene for PKU.     

Cerebrospinal Fluid and Plasma Methotrexate Levels Following High-Dose Regimen Given as a 3-Hour Intravenous Infusion in Children with Nonhodgkin's Lymphoma

In the French non Hodgkin's lymphoma protocols, central nervous system prophylaxis is provided by high-dose methotrexate (HD-MTX), given as a 3-hour IV infusion of 3 g/m² MTX along with intrathecal MTX injection. The incidence of CNS relapse is less than 3%. We designed a study to evaluate the MTX transfer across the blood brain barrier in terms of cytotoxic concentrations, during these short-term infusions. Cerebrospinal fluid and plasma MTX levels were measured during 61 courses in 29 children with non Hodgkin's lymphoma; none of them had central nervous system disease. Samples were obtained either 4, 12, 18, or 24 hours after the start of HD-MTX IV infusion. A potentially cytotoxic MTX level (10^-6 M) was reached in all courses at 4 hours (median: 2.3 × 10^-6 M) and remained available in 8/16 courses at 12 hours (median: 1.0 × 10^-6 M) and in only 2/17 courses at 18 hours (median: 0.29 × 10^-6 M). Twenty-four hours after the start of HD-MTX IV infusion, CSF MTX level was always less than 10^-6 M. The plasma MTX levels were 260, 1.3, 1.0, and 1.7 × 10^-6 M at 4, 12, 18, and 24 hours, respectively. There was no correlation between plasma and CSF MTX levels. These data show that potentially cytotoxic MTX concentrations can be reached in CSF after a 3-hour IV infusion of 3 g/m² in every patient and remain available for at least 8 hours in half of them.     

Oral mucositis and salivary methotrexate concentration in intermediate-dose methotrexate therapy for children with acute lymphoblastic leukemia

The relationship between salivary methotrexate (MTX) concentration and severity of oral mucositis after administration of MTX was investigated in six children with acute lymphoblastic leukemia. They received two administrations of MTX at 500 mg/m2 with one third given bolusly and the remainder by 24-hour continuous infusion. No significant difference among patients or administration session was observed in serum MTX concentration. Detectable concentrations of salivary MTX (greater than 0.01 microM) were observed during nine of the ten infusions. A concentration of 0.1 microM or more, apparently lasting at least 12 hours, was observed during one infusion and followed by severe mucositis. During two of the ten infusions for different patients, concentrations of 0.04 to 0.07 microM and 0.02 to 0.04 microM, apparently lasting at least 12 and 18 hours, respectively, were observed, followed by moderate mucositis. During the other seven infusions, either much shorter or no increase in salivary MTX concentration was observed, with only mild or no subsequent mucositis. Analysis by Kendall's rank method showed a statistical correlation between concentration at 6 hours of infusion and severity of oral mucositis. The findings suggest that the early secretion of MTX into saliva has a significant role in the development of oral mucositis in leukemic children.     

Degradation and clearance of methotrexate in children with osteosarcoma receiving high-dose infusion

Plasma methotrexate (MTX) concentrations were quantitated in 34 patients after 127 high-dose (35–350 mg/kg) infusions with citrovorum factor rescue. Significant linear correlations have been obtained between methotrexate dosage and concentrations in plasma at 6 and 24 hours after the initiation of the therapy. However, similar trends have not been observed when 48- and 72-hour samples were analyzed. Clinical toxicity was not serious when the methotrexate level in plasma was < 4.5 × 10^?6 M at 48 hours after the start of a six-hour infusion in children. A minimal four-hour steady-state methotrexate plasma level can be maintained during a six-hour infusion. Children excrete methotrexate at a faster rate than adults; the half-life of MTX during the first phase of plasma clearance curve is one hour shorter in children. Urinary analyses have indicated that substantial methotrexate is metabolized. The chemical nature of these components has not been identified. Further, the urinary metabolic profiles varied among patients.     

Degradation and clearance of methotrexate in children with osteosarcoma receiving high-dose infusion.

Plasma methotrexate (MTX) concentrations were quantitated in 34 patients after 127 high-dose (35--350 mg/kg) infusions with citrovorum factor rescue. Significant linear correlations have been obtained between methotrexate dosage and concentrations in plasma at 6 and 24 hours after the initiation of the therapy. However, similar trends have not been observed when 48- and 72-hour samples were analyzed. Clinical toxicity was not serious when the methotrexate level in plasma was less than 4.5 X 10(-6) M at 48 hours after the start of a six-hour infusion in children. A minimal four-hour steady-state methotrexate plasma level can be maintained during a six-hour infusion. Children excrete methotrexate at a faster rate than adults; the half-life of MTX during the first phase of plasma clearance curve is one hour shorter in children. Urinary analyses have indicated that substantial methotrexate is metabolized. The chemical nature of these components has not been identified. Further, the urinary metabolic profiles varied among patients.     

Phenylalanine hydroxylase mutations and phenylalanine-tyrosine metabolism in heterozygotes for phenylalanine hydroxylase deficiency

The aim of this study was to determine whether any relationship exists between the severity of mutation of the phenylalanine hydroxylase (PAH) gene and the plasma concentrations of phenylalanine (Phe) and tyrosine (Tyr) under fasting and semifasting conditions among heterozygotes in a matched case-control study. Parents of patients affected by PAH deficiency (n = 25) detected through the Italian Neonatal Screening Program and referred from January 1994 to June 2000, and parents of healthy children were investigated. In total, 68 subjects without any disease, 34 hyperphenylalaninaemia (HPA) heterozygous parents and 34 age- and gender-matched controls, were recruited. Plasma concentrations of Phe and Tyr in fasting and semifasting (1600 mg Phe oral load) conditions were the main outcome measures. DNA analysis for PAH mutations was performed in all 68 subjects. Compared with controls, heterozygotes showed higher fasting and semifasting Phe concentrations (p < 0.0001), lower semifasting Tyr concentrations (p = 0.015), lower Tyr variations (p = 0.003) and a higher Phe/Tyr ratio (p < 0.0001) in switching from fasting to semifasting conditions. Heterozygotes carrying a severe mutation showed semifasting plasma Tyr concentrations lower than controls (p = 0.019) but not significantly different from Tyr levels found in non-severe carriers (p = 0.197). The Tyr variations were minor in severe carriers than controls (p < 0.001) and non-severe carriers too, although with lower significance (p = 0.089). In six carriers of A403V mutation, parents of mild hyperphenylalaninaemics on an unrestricted diet, significant differences in variations from fasting to semifasting conditions were found compared with parents of patients on a diet. CONCLUSION: Although the great heterogeneity of PAH mutations limits any general conclusion, the results suggest that monitoring plasma Tyr variations may be more sensitive than plasma Phe in assessing the severity of PAH mutations in HPA heterozygotes.     

高苯丙氨酸血症患儿苯丙氨酸负荷试验后苯丙氨酸和酪氨酸浓度变化

目的了解苯丙氨酸负荷试验对高苯丙氨酸血症HPA患儿血苯丙氨酸Phe和酪氨酸Tyr浓度及其比值Phe/Tyr的影响。方法HPA组30例,非HPA儿童(对照组)33例。所有儿童均空腹口服Phe100mg/kg,分别于服Phe前0h、服Phe后1h、2h、3h、4h采手指血,滴于滤纸片上,取直径3mm干血滤纸片,经含Phe和Tyr同位素内标的甲醇萃取,盐酸正丁醇衍生,进行串联质谱分析,测定Phe、Tyr浓度和Phe/Tyr值。结果血Phe浓度HPA组于服Phe后2h最高,服Phe后4h仍维持在较高水平,对照组于服Phe后1h值最高,服Phe后4h下降至接近正常浓度,两组比较各时间段差异均有显著性(P<0.001)。Tyr浓度HPA组各时间段差异无显著性,对照组于服Phe后逐渐升高,各时间段差异有显著性P<0.05,于服Phe后2h、3h时高于HPA组,差异有显著性(P<0.05)。Phe/Tyr值HPA组各时间段均高于对照组,差异非常显著(P<0.001)。结论HPA患儿Phe代谢速度下降,测定血Phe浓度结合Phe/Tyr值有助于HPA诊断。     

Plasma and urine levels of methotrexate and 7-hydroxymethotrexate in children with all during maintenance therapy with weekly oral methotrexate

A new high-performance liquid chromatographic assay was used to determine methotrexate (MTX) and its main metabolite, 7-hydroxymethotrexate (7-OH-MTX), in the plasma (n - 17) and urine (n = 14) of children (age 3-12 years) on maintenance therapy for acute lymphocytic leukemia (n = 14) or non-Hodgkin's lymphoma (n = 3). Each child received oral doses of weekly MTX (4.0-29 mg/m²) and daily 6-mer-captopurine (40-111 mg/m²). Plasma samples were collected daily from two children during the 1-week dose interval. A limited sampling strategy was designed, whereby 2 days of blood sampling were used in the other 15 patients. Morning urine samples were collected daily for 1 week following MTX intake from 14 of the children. MTX was detectable in all plasma and urine samples for the entire dose interval. The main metabolite, 7-OH-MTX, could be detected in plasma and urine from all patients on the first day after dose intake but only in a few patients during the whole dose interval. Interpatient variability of MTX and 7-OH-MTX levels was high at all points during the week. Significant correlation were found between the urinary MTX levels on days 2 and 7 and plasma MTX levels on day 2 after intake. No significant correlation was found between drug levels in plasma or urine and liver function tests in the children showing signs of mild liver injury. This assay provides a tool for further studies on the role of pharmacokinetics for the clinical effects of weekly oral low-dose MTX given alone or in combination with 6-mercaptopurine. © 1994 Wiley-Liss, Inc.     

The course of biological parameters and 6-mercaptopurine pharmacokinetics during maintenance treatment of children with acute lymphoblastic leukaemia

Twenty patients on maintenance therapy (MT) for acute lymphoblastic leukaemia (ALL) with oral 6-mercaptopurine (6-MP) and methotrexate (MTX) were studied. White cell and red cell indices and platelets counts were monitored every second week as were drug levels. Mean values for 6-MP and MTX doses, and blood component parameters were calculated for each 6-month period for the whole patient group. 6-MP plasma concentrations and liver-function tests were determined once every six months and mean values calculated. 6-MP and MTX mean doses did not change significantly during MT. The mean area under the concentration versus time curve (AUC) 0-4 hours varied slightly from the start to the end of the MT (257 and 296 ng/ml.h, respectively). The mean plasma peak concentration increased from 98 ng/ml to 195 ng/ml (p less than 0.01) during the same period. There were significant decreases between the initial white blood cell counts (WBC) and red blood cell counts (RBC) as compared to levels at the end of therapy (p less than 0.01 and 0.02, respectively). A linear correlation was found between 6-MP peak concentrations and both WBC (r = 0.96) and RBC (r = 0.87). At the end of MT liver function tests became normal in all except 6 patients. In conclusion, MT have moderate effects on bone marrow and liver and monitoring 6-MP plasma concentration might be of value for determination of the optimal WBC levels during MT.     

The Course of Biological Parameters and 6-Mercaptopurine Pharmacokinetics during Maintenance Treatment of Children with Acute Lymphoblastic Leukaemia

ABSTRACT. Twenty patients on maintenance therapy (MT) for acute lymphoblastic leukaemia (ALL) with oral 6-mercaptopurine (6-MP) and methotrexate (MTX) were studied. White cell and red cell indices and platelets counts were monitored every second week as were drug levels. Mean values for 6-MP and MTX doses, and blood component parameters were calculated for each 6-month period for the whole patient group. 6-MP plasma concentrations and liver-function tests were determined once every six months and mean values calculated. 6-MP and MTX mean doses did not change significantly during MT. The mean area under the concentration versus time curve (AUC) 0-4 hours varied slightly from the start to the end of the MT (257 and 296 ng/ml-h, respectively). The mean plasma peak concentration increased from 98 ng/ml to 195 ng/ml ( p <0.01) during the same period. There were significant decreases betwen the initial white blood cell counts (WBC) and red blood cell counts (RBC) as compared to levels at the end of therapy ( p <0.01 and 0.02, respectively). A linear correlation was found between 6-MP peak concentrations and both WBC ( r =0.96) and RBC ( r =0.87). At the end of MT liver function tests became normal in all except 6 patients. In conclusion, MT have moderate effects on bone marrow and liver and monitoring 6-MP plasma concentration might be of value for determination of the optimal WBC levels during MT.     

Metabolic rhythms in adolescents with diabetes during treatment with porcine or human insulin.

Metabolic rhythms were studied over 24 hours in eight adolescent diabetic patients during treatment with porcine insulin and after transfer to human insulin. Despite an increase in dose with human insulin no significant changes were found in fasting blood glucose, 24h mean blood glucose, or glycosylated haemoglobin concentrations. Significantly higher 24h mean blood lactate concentrations and lower total ketone bodies and glycerol concentrations were observed during treatment with human insulin. These findings are consistent with the increase in insulin dose and do not necessarily imply different metabolic responses to species differences in insulin.     

维族、汉族急性淋巴细胞白血病患儿甲氨蝶呤不良反应探讨

目的：通过对维吾尔族及汉族急性淋巴细胞白血病（ALL）患儿甲氨蝶呤（MTX）血药浓度监测结果的分析,为MTX不良反应的发生提供判断依据。方法：根据24 h MTX血药浓度监测结果,将28例（汉族 15 例,维吾尔族 13 例）接受大剂量MTX化疗的ALL患儿分为>10 μmol/L与≤10 μmol/L组;根据48 h MTX血药浓度监测结果分为>1.0 μmol/L与≤1.0 μmol/L组。采用酶放大免疫测定法对行MTX治疗的所有患儿给药后24 h及48 h血药浓度进行检测并观察不良反应发生情况。结果：不良反应发生率在不同24 h MTX血药浓度组间差异无统计学意义(P>0.05);48 h MTX血药浓度>1.0 μmol/L组的消化道反应及黏膜损害发生率高于血药浓度≤1.0 μmol/L组 (P0.05);汉族患儿24 h及48 h MTX血药浓度均高于维吾尔族(P<0.05);除消化道反应外,汉族患儿肝功能异常、黏膜损害及骨髓抑制的发生率高于维吾尔族患儿 (P<0.05)。结论：24 h MTX血药浓度不能预测不良反应的发生,48 h MTX血药浓度对不良反应的发生有一定预测价值;24 h、48 h MTX血药浓度及不良反应发生率在维吾尔族及汉族间存在差异;MTX血药浓度监测结果可能对及时调整MTX用量,从而达到MTX个体化治疗具有重要意义。     

Newborn phenylalanine/tyrosine metabolism. Implications for screening for phenylketonuria

Controversy over the sensitivity of newborn screening for phenylketonuria (PKU) has recently led to the specific recommendation that infants discharged within the first 24 hours of life be routinely retested at 1 to 2 weeks of age. To address this controversy, data from cord blood samples, phenylalanine (Phe) tolerance tests at 3 days of age, and sequential plasma Phe determinations in six siblings of known cases of PKU or hyperphenylalaninemia were analyzed, along with data from the literature. These analyses showed that normal and probably heterozygous infants decrease their Phe concentrations with age, while infants with PKU or PKU variants increase their Phe concentrations with age but at varying rates. Predictive equations showed that the sensitivity of the screening test rapidly increases with age, so that the usual critical value of 4 mg/dL is satisfactory for suspecting PKU after 18 hours of age. A critical value of 3 mg/dL would be equally satisfactory at any age, if the Guthrie test were appropriately modified to include a 3-mg/dL standard.     

Plasma methotrexate, red blood cell methotrexate, and red blood cell folate values and outcome in children with precursor B-acute lymphoblastic leukemia: a report from the Children's Oncology Group

Plasma steady state methotrexate (MTX) level and red blood cell (RBC) MTX and folate concentrations were evaluated in 1124 children with newly diagnosed acute lymphoblastic leukemia enrolled in the Pediatric Oncology Group studies 9005 (lower risk; Regimens A and C) and 9006 (higher risk; Regimen A). These regimens included intermediate-dose MTX (1 g/m) given as a 24 hours infusion every other week for 12 doses during intensification. Plasma MTX level was evaluated at the end of MTX infusions. RBC MTX and folate concentrations were measured at the end of intensification. The 5 year continuous complete remission was 76±1.4% versus 85±3.0% for those patients with steady state MTX levels less than or equal to and greater than 14 μM, respectively (P=0.0125). Hispanic children had significantly reduced median steady state MTX levels, 8.7 μM, compared with non-Hispanic children, 9.95 μM (P=0.0015), but this did not correlate with a difference in outcome. Neither RBC MTX, RBC folate, nor the RBC MTX:folate ratio identified children at increased risk of failure.     

大剂量甲氨蝶呤目标浓度个体化调整研究

目的 探讨大剂量甲氨蝶呤(MTX)24 h输注治疗儿童急性淋巴细胞白血病目标浓度个体化调整的方法.方法 本研究涉及24例患儿105个疗程,检测MTX开始输注后第1和第6小时的血药浓度,根据已建立的大剂量MTX群体药物动力学模型,推算出该疗程稳态血药浓度(CSS)的预测值.根据CSS预测值,于MTX开始输注后第8小时调整MTX输注速度和剂量.MTX输注后第23小时再检测血药浓度(CSS实测值).结果 为达目标浓度,17例(71%)患儿进行了剂量调整.45个疗程(43%)调整了剂量,42个疗程增加了剂量,3个疗程减少了剂量.早期阶段(诱导缓解和巩固治疗方案后的大剂量MTX的疗程)29个疗程中有16个疗程增加了剂量,1个疗程减少了剂量;维持阶段76个疗程中有26个疗程增加了剂量,2个疗程减少了剂量.最终有95个(90%)疗程的CSS实测值达目标范围,8个疗程小于目标范围,2个疗程大于目标范围.如果不调整剂量,仅有74个(70%)疗程的CSS(不调整)在目标范围.调整MTX剂量,与不调整相比,可以明显增加CSS实测值达目标范围的疗程数(χ2=13.366,P=0.000).在剂量不调整的60个疗程中,CSS实测值和CSS预测值有较好的直线相关性(r=0.487,P=0.000);CSS实测值与MTX输注后第6小时的血药浓度也有一定的直线相关性(r=0.389,P=0.002).105个疗程MTX的总清除率(CL)实测值是(7.01±2.06)L/(m2·h).在所有疗程间CL相差最大达4.4倍,同一患儿不同疗程间CL相差最大达2.9倍.CL与患儿的年龄、体重和总胆红素呈直线负相关,与血磷呈直线正相关;化疗早期阶段疗程的CL有高于维持阶段疗程的倾向(P均＜0.05).结论 105个疗程大剂量MTX化疗,疗程间CL差异最大达4.4倍,需要目标浓度个体化调整.通过检测MTX输注后第1和第6小时的血药浓度,调整MTX输注速度和剂量,最终90%疗程的CSS实测值达目标范围.早期阶段大剂量MTX化疗更需要目标浓度个体化调整.     

Free and bound tryptophan in human plasma during the perinatal period.

The concentration of tryptophan and the degree of binding of the amino acid to protein were examined in human plasma during the perinatal period. Both total and unbound (free) tryptophan were higher in cord vein plasma than in the maternal circulation, the concentration gradient being approximately 1 : 2. The proportion of the total plasma tryptophan concentration that was not bound to protein was less in cord vein plasma than in the maternal circulation. After birth the proportion in infant plasma fell significantly. Both total and free tryptophan fell during the first 24 hours of postnatal life. Total tryptophan returned to the cord vein plasma level 6--8 days after birth whilst free tryptophan failed to increase during the period of the observations. In premature infants total and free tryptophan also declined in concentration 12--24 hours after birth, suggesting the phenomenon to be related to birth rather than to gestational age. Phenylalanine remained unchanged whilst tyrosine increased in concentration during the first 80 hours of postnatal life. Thus, the availability of tryptophan to the tissues appears to decline during the immediate postnatal period and the results suggest that the requirement for tryptophan during this time may exceed the supply from standard artifical milk preparations.     

FREE AND BOUND TRYPTOPHAN IN HUMAN PLASMA DURING THE PERINATAL PERIOD

Abstract. The concentration of tryptophan and the degree of binding of the amino acid to protein were examined in human plasma during the perinatal period. Both total and unbound (free) tryptophan were higher in cord vein plasma than in the maternal circulation, the concentration gradient being approximately 1: 2. The proportion of the total plasma tryptophan concentration that was not bound to protein was less in cord vein plasma than in the maternal circulation. After birth the proportion in infant plasma fell significantly. Both total and free tryptophan fell during the first 24 hours of postnatal life. Total tryptophan returned to the cord vein plasma level 6–8 days after birth whilst free tryptophan failed to increase during the period of the observations. In premature infants total and free tryptophan also declined in concentration 12–24 hours after birth, suggesting the phenomenon to be related to birth rather than to gestational age. Phenylalanine remained unchanged whilst tyrosine increased in concentration during the first 80 hours of postnatal life. Thus, the availability of tryptophan to the tissues appears to decline during the immediate postnatal period and the results suggest that the requirement for tryptophan during this time may exceed the supply from standard artifical milk preparations.     

Effects of Maternal Phenylalanine or Tyrosine Hydroxylase Inhibition on Postnatal Maturation of Catecholamine and Amino Acid Metabolism in Rats

Effects of the inhibition of maternal phenylalanine (Phe) or tyrosine (Tyr) hydroxylase on the postnatal maturation of catecholamine, thyroxine and amino acid metabolisms were examined in young rats. The intraperitoneal injections of 100 mg/kg p-chlorophenylalanine three times during the second gestational week together with 0.2% Phe solution as drinking water produced marked reduction in birth weight, body weight gain, brain weight, cerebral Tyr hydroxylase activity, adrenal epinephrine, renal norepinephrine and free amino acids in plasma and brain as well as delayed maturation of thermoregulation in the offspring. In contrast, the administration of 100 mg/kg α-methyl-p-tyrosine with 0.2% Tyr supplementation did not affect general growth, but only decreased cerebral Tyr hydroxylase and serum thyroxine level, while cerebral dopamine was increased. These results indicate that maternal Phe hydroxylase inhibition induces more severe growth failure including catecholamine and amino acid metabolism than Try hydroxylase inhibition in postnatal development.     

Metabolic events in infants of diabetic mothers during first 24 hours after birth. I. Changes in plasma glucose, insulin and glucagon

Changes in plasma glucose, nonantibody-bound insulin and glucagon concentrations were studied in 32 newborn infants of diabetic mothers (IDM) during the first 24 hours after birth. Ten infants were born to White class A mothers and 22 to class B-F mothers. The infants were kept fasting during the investigative period and blood was sampled from an umbilical artery catheter. At birth, plasma glucose and glucagon levels were similar in the class A and B-F infants, whereas nonantibody-bound insulin levels were approximately 15-fold higher in the class B-F infants than in the class A infants (p less than 0.001). After birth, plasma glucose fell in all infants, the nadir being reached at two hours (p less than 0.01). Plasma glucose fell by approximately 35% in the class A infants and 63% in the class B-F infants (p less than 0.01). Eight IDM had asymptomatic hypoglycemia (plasma glucose less than 1.9 mmol/l) and four of these infants had glucose levels below 1.7 mmol/l and were withdrawn from further study. In the remaining four hypoglycemic IDM, plasma glucose was about 1.6-fold higher (p less than 0.01) and insulin about 11-fold higher (p less than 0.001) at birth compared to the 24 normoglycemic IDM. The hypoglycemia was attended by unchanged insulin levels in the class A infants, whereas insulin fell in the class B-F infants (p less than 0.01). However, during the whole investigative period, plasma insulin of the class B-F infants was higher than that of the class A infants (p less than 0.01). After birth, plasma glucagon increased slowly in all IDM and peak values were reached after 12 hours in the class A infants (p less than 0.05) and 24 hours in the class B-F infants (p less than 0.01). Only those infants who became hypoglycemic after birth exhibited a significant increment in plasma glucagon from 0.2 hours (p less than 0.05). These results suggest that neonatal hypoglycemia of IDM results from high plasma levels of nonantibody-bound insulin together with a very retarded increment in plasma glucagon levels. The degree of neonatal hypoglycemia and hyperinsulinemia of an individual IDM seems to be positively correlated to the severity of the diabetes of the mother.