beta-Endorphin and beta-lipotropin concentrations in umbilical cord blood

Plasma-mediated immune suppression: a neonatal perspective

Plasma is a rich mixture of immune regulatory factors that shape immune cell function. This immunomodulatory role of plasma is especially important in neonates. To maintain in utero feto-maternal tolerance and to allow for microbial colonization after birth, the neonatal immune system is biased against pro-inflammatory responses while favoring immune suppression. Therefore, the neonatal period provides a unique opportunity to study the physiologic mechanisms regulating the immune system. Several recent studies in neonates have identified plasma factors that play a key role in immune regulation. Insight into immune regulation by neonatal and adult plasma may have clinical implications, because plasma is easily accessible, affordable, and widely available. Herein, we review plasma-mediated immune regulation, with specific focus on neonatal plasma. We discuss how immune suppression is a key function of plasma and provide a systematic overview of the published literature regarding plasma-derived immune suppressive proteins, lipids, purines, and sugars. Finally, we outline how immune regulation by these factors, which are particularly abundant in neonatal plasma, may eventually be used to treat immune-mediated diseases, such as autoimmune, allergic, and inflammatory diseases.

Amniotic fluid beta-endorphin: a prognostic marker for gastroschisis?

PURPOSE

The aim of this work was to study amniotic fluid beta-endorphin as a potential predictor for postnatal morbidity in gastroschisis.

METHODS

Beta-endorphin was assayed in 43 amniotic fluid samples from 13 pregnant women with fetal gastroschisis undergoing diagnostic amniocentesis or therapeutic amnioinfusion and compared with 33 controls. Within the gastroschisis group, the authors investigated the relationship between postnatal morbidity and the peak value of amniotic fluid beta-endorphin (AFBE).

RESULTS

Ten AFBE values in 6 cases of gastroschisis were above the upper limit of the 95% confidence interval derived from controls. Postnatal morbidity was significantly higher when peak AFBE exceeded 10 microg/L (n = 4 pregnancies) compared with below 5 microg/L (n = 9 pregnancies), as shown by mean duration of mechanical ventilation (15.2 v 3 days; P =.01), of parenteral feeding (77 v. 18.7 days; P =.04), and of hospitalization (84 v 32.2 days; P =.04). There was no statistically significant association between postnatal morbidity markers and prenatal dilation of fetal bowel.

CONCLUSIONS

The most severe cases of gastroschisis are associated with high levels of AFBE. The authors speculate that this fetal hormonal response could result from stress or pain caused by prenatal bowel damage.

Determinations of umbilical cord beta-endorphin concentration and blood gas parameters in newborn piglets

Neonatal mortality is a severe welfare problem in the pig industry, with the majority of neonatal deaths occurring in those piglets born later in the litter. The purpose of this study was to assess the possible link between the release of beta-endorphin, hypoxia and birth order in newborn piglets. Blood samples were taken from the umbilical cord of piglets from 16 litters at either spontaneous or cloprostenol-induced parturition. The mean (SEM) beta-endorphin concentration in cord plasma of all piglets was 276.1 (90.28)pmol litre-1 which was significantly higher than the average concentration of 73.1 (18.54)pmol litre-1 in gilts. Neither beta-endorphin nor blood gas parameters were affected by cloprostenol. A significant (P > 0.01) peak concentration of beta-endorphin was found in the piglets born four-fifths of the way through the litter. There was a significant negative correlation (P > 0.05) between cord pH and beta-endorphin concentrations. Furthermore, the concentration of beta-endorphin was positively correlated with cord pCO2 (P < 0.01). These results indicate that the release of foetal beta-endorphin is associated with the degree of acidosis in the piglets during delivery.

Umbilical cord beta-endorphin and early childhood motor development

Stress during delivery has been associated with elevated umbilical cord plasma beta-endorphin levels. Published research suggests that much cord beta-endorphin originates from fetal pituitary. Intact pituitary function is required for normal growth and development. Relationships between cord beta-endorphin and child development have not been previously reported. We measured paired maternal and cord plasma beta-endorphin concentration in a set of 106 low risk deliveries by solid phase two-site immunoradiometric assay. Geometric mean maternal and cord beta-endorphin concentrations were 128 pg/ml and 196 pg/ml, respectively, with corresponding ranges of 33-533 pg/ml and 70-579 pg/ml. Cord beta-endorphin concentration was significantly higher than maternal, regardless of delivery mode, and the two were significantly correlated (r = 0.231; P = 0.017). Multiple regression modeling showed that forceps delivery, maternal beta-endorphin concentration, bradycardia, vaginal delivery, and birth weight each made independent contributions to elevated cord beta-endorphin. Depressed cord beta-endorphin predicted more day 2 neurological soft signs, lower 6-month mental development, and lower 36-month motor score on psychometric tests of the children. Poorer fine motor control and coordination were predominantly associated with lower beta-endorphin. Level of cord beta-endorphin independent of delivery stress exerted the primary influence upon child motor development. Higher levels of stress-independent beta-endorphin may play a direct role in motor development.

Third trimester POMC disregulation predicts use of anesthesia at vaginal delivery

In a prospective study, third trimester plasma levels of BE and ACTH were determined in 58 women who delivered vaginally. Peptide regulation was compared between subjects who used conduction anesthesia at delivery and subjects who did not. Third trimester levels of maternal BE and ACTH were significantly related; however, the relationship was significant only in subjects who did not receive conduction anesthesia (n = 24) at delivery. The normal co-release pattern between BE and ACTH in subjects receiving conduction anesthesia (n = 34) during birth was uncoupled. The use of conduction analgesia during vaginal delivery was significantly related to a disregulation index created to quantify the BE-ACTH release pattern. Uncoupled ACTH and BE patterns may result from modified control of pro-opiomelanocortin (POMC) expression during pregnancy or unique proteolytic processing of POMC, and may alter pain tolerance during delivery.

Analgesics abuse: theoretical and practical considerations

Three important issues must be addressed in any attempt to determine whether combination painkillers play a role in analgesic nephropathy. The first issue, namely that of a causal link between the combination itself and nephrotoxicity, has never been adequately documented. On the contrary, there is much evidence that the combination as such has no influence whatsoever. The cause of the nephrotoxicity is most likely the painkilling mechanism, i.e. the antagonism to prostaglandins; the most potent prostaglandin-antagonists, the non-steroidal anti-inflammatory drugs, whether used in combination or singly, also most frequently cause renal pathology. The second issue, i.e. the safety of combination painkilling drugs in comparison with that of single substances, is intimately bound up with the advantages of the former with respect to both activity and the activity-side-effects ratio. The third issue, abuse, should be recast in a broader context. The central element here is not the painkilling drug but rather the labile personality of the user in conjunction with a more or less stressful environment in which a wide variety of drugs and stimulants are available and taken for better 'coping'. To a great extent analgesics abuse can be prevented by information (i.e. social medicine). In a broader perspective, man experiences considerable difficulty adapting to the sweeping social, technological and ideological changes of recent decades, and this transition contributes in no small measure to the analgesics problem. It should be a priority of government to find remedies for this state of affairs.

Beta-endorphin concentrations in fetal blood during the second half of pregnancy

OBJECTIVE

Endogenous opiates may play a role in both fetal physiologic functions and the adaptation to intrauterine stress. However, our understanding of this role is hampered by an absence of data on circulating levels of these substances during fetal life.

STUDY DESIGN

We measured serum beta-endorphin values with a radioimmunoassay in 81 paired fetal and maternal blood samples and 24 neonatal cord specimens. The former samples were uneventfully obtained from uncomplicated pregnancies between 18 and 39 weeks of gestation at the time of cordocentesis for prenatal diagnosis.

RESULTS

Mean fetal beta-endorphin concentrations were significantly lower than beta-endorphin values from neonates (90.5 pg/ml [+/- 59.4] vs 228.4 pg/ml [+/- 166.2]; p less than 0.001), but significantly higher than mean maternal values (70.5 pg/ml [+/- 48.8]; p less than 0.02). Although fetal beta-endorphin levels decreased between 18 and 28 weeks' gestation, the correlation between fetal beta-endorphin values and gestational age was not significant (r = -0.193; p = 0.07). However, fetal beta-endorphin concentrations were significantly correlated with maternal values (Spearman's rank r = 0.47; p less than 0.001).

CONCLUSION

These findings suggest that delivery or fetal adaptation to an extrauterine environment is associated with significant increases in beta-endorphin release. Moreover, although the fetal pituitary may be the primary source of circulating fetal beta-endorphin, a maternal or placental contribution cannot be excluded. Our data identify a physiologic range for fetal beta-endorphin concentrations.

Properties and functions of human placental opioid system

Human placental villus tissue contains opioid receptors and peptides. Kappa opioid receptors (the only type present in this tissue) were purified with retention of their binding properties. The purified kappa receptor is a glycoprotein with an apparent molecular weight of 63,000. Two opioid receptor mediated functions were identified in trophoblast tissue, namely regulation of acetylcholine and hormonal (human chorionic gonadotrophin and human placental lactogen) release. Placental content of kappa receptors increases with gestational age. Term placental content of kappa receptors correlates with route of delivery (higher in those abdominally obtained). Opioid use and/or abuse during pregnancy affects placental receptor content at delivery, as well as its mediated functions. Opioid peptides identified in placental extracts were beta-endorphin, methionine enkephalin, leucine enkephalin and dynorphins 1-8 and 1-13. Dynorphin 1-8 seem to be the predominant opioid peptide present in placental villus tissue.

[Acute pain in children and its treatment]

Pain in paediatrics has long been underestimated. The numerous scientific studies carried out during the last decade show that its existence can no longer be doubted: in fact, pain already exists during the neonatal period, and probably throughout the last trimester of gestation as well. Pain pathways mature during the embryonic period and peripheral receptors develop between the 7th and 20th week. A-delta and C fibers, as well as spinal roots and nerves, are completely differentiated before the end of the second month. The development of specific neurotransmitters and thalamic and cortical dendritic branching occurs later on; it is well enough developed to allow perception of painful stimuli (slow or protopathic component) from the beginning of the foetal period onwards. The discriminative rapid component develops in parallel to myelinisation, and the psycho-affective component, which requires a long and complex learning process, will not be fully operative until the end of puberty. Assessing pain, already a difficult task in the adult, is all the more so in children because of lesser verbal communicative capabilities, difficulty in handling abstract concepts, lack of experience of painful stimuli to make comparisons, and ignorance of their body image. In the very young child, diagnosing pain relies on suggestive circumstances, and an altered behaviour, knowing that no one symptom in pathognomonic. As the child grows up, methods for self-assessment of pain become usable, such as coloured scales and simplified verbal scales. However, behavioural tests remain the mainstay until the prepubertal period. The treatment of acute pain requires a reasoned approach which takes into account the state of the child, that of the aetiological investigations, the likely course of the lesions, as well as the patient's analgesic requirements. Therapeutic means do not differ from those for adult patients; however, the differences of distribution of body water, the small possibilities of linking with plasma proteins, and limited conjugation with glucuronate must be taken into account, especially during the first months of life. Local and regional anaesthetic block techniques are of great interest in elective and emergency surgery, as well as in trauma: they can provide complete pain relief, mostly without having any effect on the patient's physiological state (haemodynamics and consciousness). Peripherally acting analgesic agents, which are well supported on the whole, as well as co-analgesics, have a great part to play, although there are less drugs available than for adults. The most useful ones are paracetamol, followed by the salicylates, propionic acid derivatives and non steroid anti-inflammatory drugs.(ABSTRACT TRUNCATED AT 400 WORDS)

Umbilical cord gamma-glutamyl transpeptidase and placental dysfunction

Placental dysfunction has been suspected if human placental lactogen level and/or cystine-aminopeptidase activity were lower than 10th centile. Significant rise in gamma-glutamyl transpeptidase (GGTP) has been found in samples of arterial cord blood of newborns born to mothers with placental insufficiency. We observed the relationship between GGTP activity and decrease in cord pH and lower Apgar score of corresponding infants. We suggest that chronic hypoxemia as a consequence of placental dysfunction may result in damage of fetal liver cells.

Opioid binding properties of the purified kappa receptor from human placenta

A glycoprotein with a molecular weight of 63,000 has been purified, in an active form, from human placental villus tissue membranes. The binding properties of this glycoprotein to opioid alkaloids and peptides indicates that it is the kappa opiate receptor of human placenta. The receptor binds the tritiated ligands etorphine, bremazocine, ethylketocyclazocine and naloxone specifically and reversibly with Kd values of 3.3, 4.4, 5.1 and 7.0nM, respectively. The binding of 3H-Bremazocine to the purified receptor is inhibited by the following compounds with the corresponding Ki values EKC, 1.3 x 10(-8)M; Dynorphin 1-8, 3.03 x 10(-7); U50,488H, 4.48 x 10(-9); U69-593,2.28 x 10(-8), morphine, 4.05 x 10(-6) DADLE, 6.47 x 10(-6) and naloxone, 2.64 x 10(-8). The purified receptor binds 8 nmole of 3H-Etorphine and 1.7 nmole 3H-BZC per mg protein. The theoretical binding capacity of a protein of this molecular weight is 15.8. Although the iodinated purified receptor appears by autoradiography as one band on SDS-PAGE, yet homogeneity of the preparation is not claimed.

Correlation between plasma levels of ACTH and beta-endorphin in the first seven days of postnatal life

Plasma adrenocorticotropic hormone (ACTH) and beta-endorphin (beta-EP) concentrations were measured by radioimmunoassay in 122 newborns, born vaginally after spontaneous labor between the 38th and the 41st week of pregnancy. Blood samples were taken from umbilical cord in 10 newborns and from antecubital vein in the remaining 112 newborns, divided into 8 groups aged from 12 h to 7 days. The mean (+/- SE) ACTH concentrations in cord plasma were 81.87 +/- 10.16 pg/ml and decreased significantly (p less than 0.01) at the 24th h of life (49.09 +/- 6.93 pg/ml). Afterwards mean ACTH plasma concentrations fluctuated around the latter values. The mean (+/- SE) B-EP concentrations in cord plasma were 21.96 +/- 3.12 pmol/l and decreased significantly at the 24th h of life (13.43 +/- 2.08 pmol/l; p less than 0.01). From the 24th h to the 7th day the mean plasma concentrations of beta-EP were not significantly different. ACTH and beta-EP plasma levels were positively correlated (p less than 0.001) at delivery and during the first seven days of life.

Plasma immunoreactive beta-endorphin, ACTH and cortisol concentrations in mothers and their neonates immediately after delivery--their relationship to the duration of labor

In 29 cases of vaginal delivery with normal outcome and 4 cases of cesarean section, the concentrations of beta-endorphin, ACTH and cortisol were determined in maternal venous and umbilical venous plasma immediately postpartum. According to duration of labor and mode of delivery the cases examined were classified into three groups: Group A (18 cases) = vaginal delivery of less than 10 hours' duration, Group B (11 cases) = vaginal delivery of more than 10 hours' duration of labor, Group C (4 cases) = cesarean section under general anesthesia. With the exception of one, the deliveries took place at term. The 33 neonates were in a very good clinical state 5 minutes after parturition (11 Saling points as median value). For measurement of the hormone concentrations radioimmunoassays were used. In Group a the mean beta-endorphin concentration in maternal plasma amounted to 150.9 +/- 16.3 pg/ml, that in neonatal plasma to 239.2 +/- 23.5 pg/ml (means +/- SEM). In Group B plasma beta-endorphin, both maternal and neonatal, was slightly higher than in Group A: 153.0 +/- 12.0 pg/ml (maternal) and 260.9 +/- 37.1 pg/ml (neonatal). The differences between maternal and neonatal beta-endorphin levels were statistically significant: Group A p less than 0.01, Group B p less than 0.05; chi 2-test. The mean ACTH concentrations in the plasma of the newborn infants were also found to be considerably higher compared with those in the plasma of their mothers: Group A 78.2 +/- 16.5 pg/ml (maternal) and 98.0 +/- 23.3 pg/ml (neonatal); Group B 98.0 +/- 20.1 pg/ml (maternal) and 165.8 +/- 39.6 pg/ml (neonatal).(ABSTRACT TRUNCATED AT 250 WORDS)

Persisting subsensitivity of the striatal dopamine system after fetal exposure to beta-endorphin

Fetal exposure of rats to beta-endorphin during the third trimester, either alone or with alpha-MSH, resulted in mild developmental delay and significant decreases in striatal dopamine receptor density (subsensitivity) persisting through maturity. The apparent paradoxical down-regulation of dopamine receptors in the presence of beta-endorphin was consistent with fetal exposure to dopamine receptor antagonists and synthesis inhibitors. These findings suggest biophysical properties of receptors which are unique to fetal development including loss of plasticity after exposure to antagonists. Permanent, down-regulation of the striatal dopamine system may be one mechanism underlying delayed development after fetal exposure to beta-endorphin which may accompany hypoxia. Even though there were no statistically significant differences between males and females in density of the dopamine receptor, the behavioral profile after peptide treatment was sexually demorphic. Behaviorally, female rats appeared sensitized to perinatal alpha-MSH and males to alpha-endorphin.

Correlation between the number of placental opioid receptors, mode of delivery, and maternal narcotic use

Human placental opioid receptors were assayed using the radioactive opioid agonist, etorphine, to determine the number of binding sites in villous tissue membrane preparations. Significant differences in receptor concentration per milligram of protein of tissue were found between placentas obtained following vaginal or abdominal delivery (P less than 0.002). Labor itself did not alter apparent receptor numbers. In patients with maternal narcotic abuse during pregnancy, no opioid binding could be detected regardless of the mode of delivery, suggesting possible receptor down-regulation.

Maternal and fetal beta-endorphin release in response to the stress of labor and delivery

In order to clarify the stress effect of labor on maternal and neonatal plasma levels of beta-endorphin, we measured this peptide in samples taken from 40 pregnant patients and their neonates at the time of normal vaginal delivery (n = 15), and at cesarean section performed either in early labor (n = 13) or prior to labor (n = 12). The mean (+/- SE) maternal plasma concentration of beta-endorphin in the vaginal delivery group was 40.3 +/- 5.6 fmol/ml, which was significantly higher than that in their neonates (21.3 +/- 2.9 fmol/ml). In contrast, maternal levels of beta-endorphin in the cesarean section groups (8.2 +/- 1.2 and 8.5 +/- fmol/ml) were significantly lower than those in their neonates (23.3 +/- 5.6 and 15.6 +/- 2.8 fmol/ml). Concentrations of beta-endorphin in mothers delivered vaginally were also significantly higher than those in mothers delivered by cesarean section. However, there was no difference in mean cord levels of beta-endorphin among the three groups. These findings indicate that neither the presence or absence of labor affects fetal plasma beta-endorphin secretion and the stress of labor and delivery produces a marked increase in maternal release of beta-endorphin.

Plasma and red blood cell beta-endorphin immunoreactivity in normal and complicated pregnancies: gestational age variation

Recent observations suggest that there may be two pools of beta-endorphin-like immunoreactivity in mammalian circulation. One of these pools is present in plasma and the other is detected in association with erythrocytes. Elucidation of an erythrocyte-associated pool may explain some of the wide variability of plasma beta-endorphin levels reported in the literature. We measured beta-endorphin immunoreactivity levels in 85 normal and 33 complicated pregnancies to delineate a possible correlation between gestational age and beta-endorphin immunoreactivity levels in plasma and in erythrocytes. Our results indicate that beta-endorphin immunoreactivity levels in both plasma and erythrocytes vary systematically throughout the gestational period, reaching a peak at 31 to 32 weeks of gestation. Amniotic fluids at midgestation were also analyzed and no correlation was observed between the levels of beta-endorphin immunoreactivity and fetal sex. Compared to normal patients, diabetic patients had significantly lower levels of beta-endorphin immunoreactivity in plasma and higher levels in erythrocytes although the total beta-endorphin immunoreactivity was not statistically different from that in normal subjects. We conclude that (1) the total beta-endorphin immunoreactivity level in whole blood is much higher than that reported in plasma, (2) both plasma- and erythrocyte-associated beta-endorphin immunoreactivity levels vary with gestational age, with a peak level at 24 to 32 weeks of gestation, (3) amniotic fluid beta-endorphin immunoreactivity levels are unrelated to fetal sex, and (4) diabetic patients may have a different distribution of beta-endorphin immunoreactivity pools than normal individuals.

Plasma immunoreactive beta-endorphin and cortisol in the newborn infant after elective caesarean section and after spontaneous labour

The effect of the mode of delivery on the plasma concentration of immunoreactive beta-endorphin (irbeta-E) and cortisol was studied in 27 newborn infants, 10 delivered by caesarean section and 17 by spontaneous vaginal labour. After elective caesarean section, the mean plasma concentration of cortisol rose from 227 +/- 27 nmol/l (S.E.) at birth to 705 +/- 90 nmol/l at the age of 2 h, indicating a significant increase in cortisol secretion, and the mean irbeta-E remained high, being 111 +/- 24 ng/l at birth and 117 +/- 21 ng/l at the age of 2 h. After spontaneous labour, the plasma cortisol level was already high at birth, 735 +/- 78 nmol/l, and remained so to the age of 2 h, 659 +/- 43 nmol/l, whereas the plasma irbeta-E decreased from 181 +/- 29 at birth to 64 +/- 7 ng/l at the age of 2 h. All newborns were in a good condition except one in whom transitory tachypnea developed during the follow-up. In this newborn the plasma level of irbeta-E increased greatly: from 210 ng/l to 705 ng/l. These results show that, irrespective of the route, the delivery is stressfull to the newborn infant. In newborns delivered by caesarean section the stress response comes after birth. Additional stress such as respiratory difficulties seems to increase the secretion of beta-endorphin.

Plasma beta-endorphin concentrations prior to and during pregnancy, in labor, and after delivery

Beta-Endorphin was measured by radioimmunoassay in peripheral plasma of nonpregnant women (58 +/- 2.4 pg/ml, n = 17, mean +/- SE), during the first trimester (47 +/- 2.4 pg/ml, n = 11), the second trimester (33 +/- 1.9, n = 11), and the third trimester (49 +/- 2.7 pg/ml, n = 10) of pregnancy, during early (202 +/- 32 pg/ml, n = 12) and advanced labor (389 +/- 78 pg/ml, n = 10), and 30 to 60 minutes post partum (177 +/- 22 pg/ml, n = 12). Mean plasma levels of beta-endorphin were significantly lower in each trimester of gestation than the levels in nonpregnant control subjects. During labor and the early postpartum period, maternal plasma levels of beta-endorphin were significantly elevated. Furthermore, peripheral plasma levels of beta-endorphin during labor fell from 189 +/- 31 to 97.6 +/- 12 pg/ml (n = 13, p = 0.015) in response to epidural anesthesia, as compared to peripheral plasma concentrations of beta-endorphin of 223 +/- 71 and 193 +/- 47 pg/ml prior to and after injection of saline solution into epidural catheters, respectively, in 10 control subjects. Mean plasma levels of beta-endorphin in patients immediately prior to elective repeat cesarean section who were not in labor (151 +/- 23 pg/ml, n = 15) were significantly higher (p less than 0.005) than the levels in third-trimester control subjects. These data indicate that the pain associated with labor and the psychological stress of anticipating an operation are potent stimuli for the pituitary release of beta-endorphin.

Opiates, endorphins, and the developing organism: a comprehensive bibliography, 1982-1983

A comprehensive bibliography of the literature concerned with opiates, endorphins, and the developing organism for 1982 and 1983 is presented. Utilized with a companion paper (Neurosci Biobehav Rev 6: 439-479, 1982) these articles cover clinical and laboratory references beginning in 1875. For the years 1982 and 1983, a total of 385 citations was recorded. A series of indexes accompanies the citations in order to make the literature more accessible. These indexes are divided into clinical and laboratory topics. The clinical section is subdivided into: age of subject examined, maternal aspects, the fetus, and the offspring. The laboratory section is subdivided into: type of opiate/endorphin studied, species utilized, and major subject areas explored.

Effect of intrathecal morphine during labor on maternal plasma beta-endorphin levels

Plasma beta-endorphin was measured in 16 patients in labor prior to and after complete onset of analgesia with 1 mg of morphine administered intrathecally. Human beta-endorphin levels were determined by radioimmunoassay following silicic acid extraction of plasma samples and separation of the beta-endorphin fraction by gel chromatography. Plasma beta-endorphin levels decreased significantly (p less than 0.005) after intrathecal morphine from 76 +/- 9.7 to 46.3 +/- 9.1 fmol/ml (mean +/- SE), possibly because of decreased pituitary beta-endorphin secretion in response to alleviation of labor pain.

A double blind trial of naloxone in the treatment of acute stroke

Naloxone has been reported to have potential benefit in the treatment of stroke. We evaluated the effect of naloxone in a double-blind trial conducted with 15 stroke patients whose deficits ranged from 8 to 60 hours in duration. All but one patient sustained a cerebral infarction. Neurologic function was assessed before and five minutes after each of two injections given to each patient in a double-blind fashion. The injections consisted of naloxone (0.4 mg in 3 patients and 4.0 mg in 12 patients) and saline. Prior to the trial, samples of plasma were obtained for determination of immunoreactive beta-endorphin for each patient. Four patients showed minimal improvement following injection of naloxone, while five patients exhibited a slightly greater improvement following saline injection. There were no significant elevations of plasma beta-endorphin among stroke patients. We conclude that naloxone may not have a significant therapeutic role for stroke in the clinical setting.

Beta-endorphin in pregnancy

Concentrations of maternal plasma beta-endorphin (beta-EP) as measured by radioimmunoassay decline during pregnancy, reaching a nadir during the second trimester, rise during labor, remain elevated during the early postpartum period and are increased prior to elective cesarean section in the absence of labor. They decline in response to epidural anesthesia during labor and increase during induction of general but not regional anesthesia for cesarean section. Umbilical venous plasma beta-EP levels are not affected by the route or mode of delivery nor the presence or absence of labor, but rise in conjunction with fetal distress. In the presence of fetal distress, umbilical arterial plasma beta-EP levels appear to rise faster than umbilical venous beta-EP concentrations. Amniotic fluid beta-EP levels are higher during the second than third trimester. These data indicate that peripheral plasma beta-EP concentrations reflect stress in both mother and fetus. In the mother, pregnancy itself does not appear to be stressful, whereas pain associated with labor rather than uterine contractions as such increase plasma beta-EP levels. In the fetus, hypoxia and acidosis effectively raise plasma beta-EP concentrations. The origin and physiologic significance of amniotic fluid beta-EP, which appears to be unrelated to fetal maturity, remain to be established.

Effects of induction of general and regional anesthesia for cesarean section on maternal plasma beta-endorphin levels

Plasma beta-endorphin was measured in 40 healthy pregnant women undergoing cesarean section. Group 1 patients (N = 14) received general anesthesia by rapid-sequence induction and endotracheal intubation with curare, thiopental, and succinylcholine. Anesthesia was maintained with nitrous oxide, oxygen, and muscle relaxant until delivery. Group 2 patients (N = 26) received regional anesthesia (spinal, 14, and epidural, 12). Maternal blood samples were drawn from indwelling venous catheters prior to and after induction of either general or regional anesthesia. Plasma beta-endorphin was determined by radioimmunoassay following silicic acid extraction and gel chromatography. In the 14 patients who underwent general anesthesia, the mean (+/- SEM) plasma beta-endorphin increased significantly (p less than 0.025) from 46 +/- 7.4 to 111.6 +/- 8.9 fmol/ml. There was no significant change in plasma beta-endorphin level of the 26 patients who underwent regional anesthesia; beta-endorphin levels averaged 44.5 +/- 5.1 and 47.6 +/- 4.8 fmol/ml prior to and after induction of anesthesia, respectively. These data demonstrate that plasma beta-endorphin concentrations are elevated following induction of general anesthesia but not with induction of regional anesthesia, which suggests that less stress is associated with regional than with general anesthesia induction in patients undergoing cesarean section.

Amniotic fluid beta-endorphin and beta-lipotropin concentrations during the second and third trimesters

Amniotic fluid beta-endorphin (beta-EP) and beta-lipotropin (beta-LPH) were measured by radioimmunoassay after silicic acid extraction and gel chromatographic separation of the two peptides in uncomplicated second-trimester and term pregnancies, in diabetic patients at term, and in pregnancies complicated by Rh-isoimmunization, premature labor, and intrauterine growth retardation. Furthermore, the lecithin/sphingomyelin (L/S) ratios as well as the dehydroepiandrosterone sulfate (DHEA-S) and cortisol levels were determined in most of the amniotic fluid specimens. Both the mean (+/- SE) beta-EP (65.3 +/- 9.1 fmol/ml) and beta-LPH (150 +/- 15.8 fmol/ml) concentrations were significantly higher in the 20 patients with normal pregnancies of 16 to 21 weeks' duration than those found in 21 patients with uncomplicated term pregnancies of 38 weeks' gestation, averaging 42.6 +/- 6.0 and 80.1 +/- 10.7 fmol/ml, respectively. The mean amniotic fluid beta-EP and beta-LPH concentrations measured in the latter subjects were similar to those observed in 23 diabetic patients with otherwise uncomplicated term pregnancies. The mean amniotic fluid beta-EP and beta-LPH levels found in the limited number of patients with Rh-isoimmunization (N = 9), premature labor (n = 8), and intrauterine growth retardation (n = 5) with pregnancies of 24 to 36, 24 to 36, and 34 to 38 weeks' gestation, respectively, were not significantly different from the mean amniotic fluid beta-EP and beta-LPH concentrations of uncomplicated term pregnancies. In all patients but those with Rh-isoimmunization, beta-EP concentrations exhibited a positive correlation with beta-LPH levels. However, the molar beta-LPH:beta-EP ratio was significantly lower at term than during the early second trimester. Neither beta-EP nor beta-LPH correlated with the amniotic fluid L/S ratio and only beta-LPH exhibited a significant inverse correlation with amniotic fluid DHEA-S. The latter was significantly higher in uncomplicated term than second-trimester pregnancies. These results confirm that immunoassayable beta-EP is present in amniotic fluid and declines toward term. These data demonstrate that immunoassayable beta-LPH is present in amniotic fluid and show a more pronounced decrease toward the end of pregnancy than beta-EP. Neither peptide, at least on account of the amniotic fluid levels, appears to be associated with fetal maturation. The physiologic significance of amniotic fluid beta-EP and beta-LPH and their possible role as markers of fetal response to stress remain to be elucidated.

Endogenous opiates: 1982

This article is the fifth installment in an annual series of reviews of successive year's research dealing with the endogenous opiate peptides. Due to the continuing massive increase in the number of studies in this field, it has become impossible to continue comprehensive reviews of all aspects of this work. As a result we have decided that beginning this year the coverage will be abbreviated to emphasize non-analgesic and behavioral work. The specific areas discussed include stress, tolerance and dependence, consummatory responses, alcohol consumption, schizophrenia and emotional disorders, learning and memory, cardiovascular responses, respiratory effects, thermoregulatory effects, neurological deficits and other disorders, activity, and other, miscellaneous behaviors. As in previous years, we have attempted a relatively comprehensive review of the subjects covered only for the previous year and have not made an attempt to evaluate their contributions relative to those of past years.