Combined high-performance liquid chromatography-radioimmunoassay for the characterization and quantitative measurement of neuropeptides

A method for the extraction, separation, characterization and quantitation of angiotensins, opioid peptides and several other neuropeptides in biological samples is described. Gradient elution in different reversed-phase high-performance liquid chromatographic systems gives high resolution with constant recoveries between 60 and 70%, allows UV detection at 220 nm and is compatible with radioimmunoassay. The method is highly reproducible and applicable to the characterization and quantitative measurement of peptides in the femtomolar range. The practicability of the method is demonstrated for angiotensin peptides in plasma, brain and peripheral organs, as well as for opioid peptides in the heart.

Oxytocin unlike vasopressin is a stress hormone in the rat

The functions of oxytocin in the female are thought to be confined to the processes of milk ejection and parturition. In this study the role of oxytocin in the body's response to stressful stimuli has been examined. Physical immobilization of rats and forced swimming caused large increases in the secretion of the hormone, whereas vasopressin levels remained unchanged. These findings classify oxytocin, in contrast to vasopressin, as a so-called 'stress hormone' and suggest its importance in processes other than those related to reproduction.

The brain angiotensin system: subcellular localization and interferences with converting enzyme inhibitors

Renin is stored in synaptosomes of rat brain, separately from cathepsin D and intraneuronal angiotensin II (ANG II) has been demonstrated with the electron-microscope. Although the subcellular localization of other components of the renin-angiotensin system (RAS) have still to be investigated, these data suggest possible intracellular synthesis of ANG II in the brain. Brain ANG II is biochemically identical to the plasma peptide and corresponds to (IIe) 5-ANG II. The peptide level is unchanged after bilateral nephrectomy, and angiotensin I (ANG I) accumulation is observed in nephrectomized animals following brain angiotensin converting enzyme blockade. The significantly greater accumulation of ANG I and reduction of ANG II in stroke prone spontaneously hypertensive Wistar-Kyoto rats (WKY) indicates a higher synthesis and turnover rate of ANG II in SHR. Most converting enzyme inhibitors (CEI) penetrate the brain after chronic oral treatment. Part of their blood pressure lowering action may therefore be explained by an inhibition of the brain RAS.

Angiotensin synthesis in the brain and increased turnover in hypertensive rats

The missing link in the evidence for an active endogenous renin angiotensin system in the brain has been the demonstration of local angiotensin synthesis in the central nervous system in vivo. In this report the extraction and characterization of angiotensin I and angiotensin II from the brain of rats is described. The accumulation of angiotensin I was enhanced in hypertensive rats when the conversion to angiotensin II was blocked in vivo by the converting enzyme inhibitor captopril.

N-terminal peptide of pro-opiomelanocortin in human amniotic fluid

N-terminal peptide of pro-opiomelanocortin (N-POMC) was measured in the human amniotic fluid. At the gestational age of 16 to 20 weeks, the radioimmunoassay with three different antibodies demonstrated the respective values of 2.39 +/- 0.78, 4.69 +/- 2.27, and 5.92 +/- 2.66 ng/ml. These values are approximately 10 times higher than the measurements in the plasma of women at the corresponding gestational period. The amniotic fluid collected during the delivery had significantly lower concentrations of N-POMC than the amniotic fluid at 16 to 20 weeks' gestation. However, the plasma values of N-POMC had increased approximately three times when measured at delivery and compared with the plasma values at 16 to 20 weeks' gestation. Adrenocorticotropic hormone, measured simultaneously with N-POMC in some of the samples, showed changes similar to those in N-POMC. The N-POMC immunoreactivity from the amniotic fluid has the same retention time on reversed-phase high-performance liquid chromatographic separation as the peptide purified from the human pituitary gland, thus indicating the identity of both peptides.

Effects of lesions in the paraventricular nucleus of the hypothalamus on vasopressin and oxytocin contents in brainstem and spinal cord of rat

The effects of lesions of the paraventricular nucleus in rat hypothalamus (PVN) on the vasopressin (AVP) and oxytocin (OT) contents of the brainstem and spinal cord, as measured by radioimmunoassay, were studied. AVP decreased by 50% and 80% in brainstem and spinal cord of lesioned animals, whereas OT disappeared almost completely. Therefore, in contrast to OT, the PVN is not the only site of origin of AVP-containing nerve fibers projecting to the brainstem.

Evidence for the presence of enkephalins in the heart

Extracts of guinea pig hearts were subjected to high performance liquid chromatography (HPLC) and the eluted fractions monitored by radioimmunoassays (RIA) for their content of leucine5-enkephalin (Leu-ENK) and methionine5 enkephalin (Met-ENK). Distinct peaks of both Leu-ENK and Met-ENK immunoreactivity were found corresponding to the position of synthetic Leu-ENK and Met-ENK respectively. The ratio of Leu-ENK to Met-ENK content was about 1:4. Chemical sympathectomy with 5-hydroxydopamine (6-OH-DA) produced a dramatic fall in noradrenaline content of the heart by more than 99%, whereas the concentration in Leu-ENK was reduced by only 70%. The Leu-ENK content of the adrenal glands was not affected by this treatment. These observations point to an enkephalinergic innervation of the heart which appears to be mainly of sympathetic origin. The results suggest the participation of enkephalins in cardiac reflex mechanisms.

The tissue renin-angiotensin systems: focus on brain angiotensin, adrenal gland and arterial wall

The enzyme renin has long been considered an exclusively renal enzyme responsible for the generation of angiotensin in the plasma, and angiotensin was considered a peptide hormone with specific target organs. Since renin has been discovered to occur not only in the kidney but in addition in a large number of other tissues, e.g. the salivary gland, the uterus, the blood vessels, the adrenal gland and the brain, this concept had to be revised. The possibility of local generation of angiotensin in these target tissues, where it has marked biological effects casts a new light on angiotensin as a more ubiquitous tissue factor or even a neurohormone.

Kininogenase activity in rat uterus homogenates

A synthetic peptide substrate for tissue kallikreins was hydrolysed by uterus homogenates. These also released kinins when incubated with dog kininogen. By using high pressure liquid chromatography in combination with a radioimmunoassay for kinins, the peptides released were identified as bradykinin and kallidin. Plasma kallikrein and trypsin released bradykinin from dog kininogen and hog pancreas kallikrein released kallidin from this substrate. This suggests that a tissue kallikrein and also a trypsin-like enzyme or perhaps plasma kallikrein are present in rat uterus.

Distribution of neurophysins in rat brain: radioimmunological measurement and characterization

Rat neurophysins were isolated from posterior pituitaries and antibodies raised in rabbits. Individual sensitive and specific radioimmunoassays for the neurophysins associated with either vasopressin or oxytocin were developed and employed for measuring the neurophysins in various regions of rat brain. Neurophysin-like immunoreactivity was detected in hypothalamus, septum, amygdala, brainstem and spinal cord. Characterization by high performance liquid chromatography suggested the identity with the neurophysins contained in the posterior pituitary. The distribution of these peptides in the brain points to a possible role in central nervous system processes.

[Experience in the care of a pregnant woman known to be carrying a mongoloid fetus (author's transl)]

This is a report on a 43-year-old woman in whom a mongoloid fetus could be diagnosed at the 26th week of pregnancy, following amniocentesis in the 23rd week. The interruption of pregnancy at first desired was later refused by the patient for reasons of conscience and the pregnancy carried to term. The lessons and conclusions to be drawn from this case are discussed.

Thyroid disease following the administration of thorotrast

Four cases of thyrotoxicosis are reported among 35 patients who had been given Thorotrast during the investigation of intracranial haemorrhage. For the group as a whole Thorotrast had been given between 11 and 31 years (mean 23.4 years) before this study. Thyrotoxicosis occurred in four patients between six and 17 years (mean 11.8 years) after the injection of Thorotrast. The fact that thyrotoxicosis did not occur in a small control group of patients who had had a subarachnoid haemorrhage and in whom Thorotrast had not been used at angiography suggests that Thorotrast may be of aetiological significance. In view of the known association between thyrotoxicosis and changes in the lymphoreticular system it is possible that the irradiation of this system by retained thorium has resulted in an abnormality of function which renders these patients more liable to the development of thyrotoxicosis.A fifth patient developed non-toxic thyroid enlargement 16 years after Thorotrast angiography.