Plasma levels of oxytocin and vasopressin before, during and after parturition in cows

In cows, plasma oxytocin and vasopressin were determined by specific and sensitive radioimmunoassays before, during and after parturition. In no case, oxytocin is elevated until the forelimbs of the foetus were distending the vagina and presenting at the vulva, supporting the view that endogenous maternal oxytocin does not primarily induce parturition. This finding is confirmed by simultaneous recording of myometrial electrical activity in 3 animals. Maximal oxytocin levels of 60.4 to 116 pg/ml plasma were measured at delivery of the foetus. The elevation in plasma vasopressin (peak values at delivery: 4.74 to 41.5 pg/ml) might be due, at least partially, to the increase in plasma osmolality during parturition.

Some observations indicating a low brain uptake of [3H]Nle11-Substance P

The studies concerning the problem of whether an exogenous neuropeptide is able to enter the brain tissue were extended to the undecapeptide Substance P (SP). The amount of radioactivity 15 s after intracarotid injection of [3H] Nle11-SP or [14C] inulin was determined in 18 brain regions and the anterior pituitary of male rats. As compared to the reference [14C] inulin (mean +/- SD: 0.143 +/- 0.009% of the injected radioactivity per g tissue wet weight), the amount of radioactivity was higher after [3H]Nle11-SP injection (0.233 +/- 0.039%, p less than 0.001). Statistically significant differences could be found particularly in cortical and caudal areas as well as in the circumventricular organs studied. These observations do not refute the assumption that a low brain uptake of the labelled neuropeptide occurred due to an accumulation within structures of the blood-brain barrier and/or a penetration of the barrier system.

Crossover study with human insulin (recombinant DNA) in type I diabetic subjects

The activity of three combinations of regular and NPH human insulin (recombinant DNA) has been compared to that of an intermediate-acting pork insulin in a crossover study in type I diabetic subjects. After a prephase, the patients injected each insulin subcutaneously for 1 wk in different order. During the 5-wk period, daily glucose profiles were self-monitored, except at the end of each week, when blood was sampled for the determination of glucose, HbA1, glycosylated albumin, C-peptide, glucagon, and routine laboratory parameters. Fasting as well as mean daily glucose and mean amplitude of glucose excursions were similar during the treatment with pork and the various human insulin preparations. There was also no significant difference in C-peptide, glucagon, HbA1 or the routine laboratory parameters with each insulin tested. Glycosylated albumin, however, was significantly lower during the test period with intermediate-acting pork insulin and human insulin (25:75 regular:NPH), when compared with the prephase. We conclude that in type I diabetic subjects human insulin in special galenic preparations shows very similar metabolic activity to pork insulin.

[Islet cell cancer with organic hyperinsulinism. Clinical aspects, diagnosis and therapy]

About 8%-15% of the patients with organic hyperinsulinism have an islet cell carcinoma (13% in our series). In addition to a history of complaints of relatively recent onset, the patients present clinically the typical intermittent neurologic-psychiatric symptoms concurrently associated with hypoglycemia. The diagnosis is established biochemically on the basis of hypoglycemia, with inadequate incrementation of the insulin concentration subsequent to suppression and provocation tests. Elevated serum proinsulin and, in most patients, an increased insulin secretion rate are usually found after administration of agents such as glucose or leucine. Localization of the tumors is achieved by selective coeliacography as well as abdominal computerized axial tomography. The islet cell carcinoma is found most frequently in the tail of the pancreas, less frequently in the body and head of the pancreas. Metastatic spread is seen early into adjacent lymph nodes and especially in the liver. The treatment of choice is surgical resection of the tumor. Even in cases with advanced metastatic involvement, surgical intervention appears indicated. Medical treatment includes the administration of diazoxide, long-acting glucagon as well as the cytostatic agent streptozotocin. The average survival time is 30-40 months after diagnosis (in our series 79 months). Thus, the prognosis of patients with islet cell carcinoma appears relatively favorable, especially when compared with adenocarcinoma of the pancreas.

Plasma vasopressin and oxytocin in response to exercise and during a day-night cycle in man

Plasma vasopressin (AVP) and oxytocin (OXT) were determined by radioimmunoassay in healthy young men before, during and after a running exercise until exhaustion. In four of the five test subjects (one subject was underloaded) physical load resulted in a marked increase in plasma AVP with peak values of 11.7 to 57.8 pg/ml at exhaustion. Plasma OXT increased in three test subjects with peak values of 4.5 to 23.9 pg/ml. Within 1 h of recovery, both neuropeptides returned to basal plasma levels. The relationship between plasma AVP and osmolality (p less than 0.001) suggests that changes in osmolality play a dominant role in regulating the secretion of AVP. Besides peripheral effects, the increased levels of AVP and/or OXT during and immediately after the exercise, respectively, might induce a favourable action on the brain function. Determination of plasma AVP and OXT during a day-night cycle in the same test subjects reveals increased AVP levels from 02.00 to 08.00 h as compared to the other time periods chosen (18.00--24.00 h, p less than 0.001; 08.00--16.00 h, p = 0.031). In contrast, OXT does not differ between these time periods but decreased from 08.00 to 16.00 h (p less than 0.01). Accordingly, no correlation exists between both neuropeptides suggesting an independent secretion. It is unclear whether the circadian variations shown are able to influence the neuropeptide response to exercise.

Simultaneous measurement of arginine vasopressin and oxytocin in plasma and neurohypophyses by radioimmunoassay

Arginine vasopressin (AVP) and oxytocin (OXT) were measured simultaneously in the same sample by specific and sensitive radioimmunoassay (RIAs). The antibodies used did not cross-react to a variety of analogues and related peptides. The extraction procedure using Vycor glass powder resulted in mean recoveries of 84.4% (AVP) and 64.6% (OXT). In both assays, the sensitivity was 1 to 2 pg/ml plasma. A preincubation procedure that depresses plasma levels of both AVP and OXT selectively, provided specific blank values for a given plasma sample. To confirm the validity of the RIAs, dehydration experiments were performed. In rats, the basal levels of plasma AVP and OXT (means: 2.63 pg/ml and 6.80 pg/ml, respectively) are increased significantly after 24 h, 48 h and 72 h of water deprivation. Relationships are presented between both neurohormones in the plasma and neurohypophyses of control and dehydrated animals. As shown in cows, a significant correlation exists between plasma AVP and plasma osmolality but not between plasma OXT and osmolality or plasma AVP and OXT. The conclusion is drawn that basal levels as well as physiological changes in plasma and neurohypophyseal AVP and OXT can be measured by the RIAs described.

[Effect of caerulein on blood glucose, serum insulin, glucagon, prolactin and growth hormone before and after oral glucose load in healthy volunteers and diabetic patients (author's transl)]

Eleven healthy volunteers, five type I diabetics, and one type II diabetic man were examined. After an overnight fast caerulein (20 ng/kg) was injected intravenously and 60 min later an oral glucose tolerance test was performed with 100 g glucose in the normals and 25 g glucose in the diabetics. Blood pressure, pulse rate, blood glucose, serum insulin, glucagon, prolactin and growth hormone values were measured during the whole period of 240 min and compared with the same parameters in control tests in the same persons without caerulein application. None of the measured parameters were significantly influenced by caerulein. It is therefore concluded that in contrast to the stimulation of the exocrine pancreas functions of the endocrine pancreas, the pituitary gland and glucose tolerance are unchanged after caerulein.

[Disease picture and operative therapy in multiple endocrine adenomatoses (MEA sydrome)]

We have outlined the symptoms, diagnostic procedures and operative treatment of "multiple endocrine adenomatosis" (MEA I, IIa und IIb). The priority of the operative procedure whenever two or more clinical syndromes in a patient with MEA are present and the possibility of multiple tumors has to be considered carefully. When there is a tumor of an endocrine organ, it should always bethought about the MEA-syndrome. We report about 9 patients seen in our hospital.

[Exocrine pancreatic secretion, gastrin and insulin in men by intraduodenal bolus injection of calcium (author's transl)]

The possible role of calcium in human bile during the biliary stimulated exocrine pancreatic secretion was investigated in 15 healthy volunteers. Total outputs of trypsin, bicarbonate, bilirubin and volume in the duodenal juice and serum gastrin were measured during a continuous intravenous infusion of secretion (0.5 CHR U/kg/h) for 40 min. The same parameters were determined after a single intraduodenal dose of Ca++ (20 ml 13,5, 135 or 270 mval/l, n = 5 for each dose) and compared with aequivalent intraduodenal dose of Na+ and an intravenous dose of secretion/cholecystokinin (1 CHR and IDU U/kg). Low calcium (13,5 mval/l) had no effect on the output of pancreatic enzymes and bile. However the higher doses led to a significant increases of the outputs of trypsin and bilirubin, which was about 75% of the enhancement seen with secretin/cholecystokinin in the dose used. Serumgastrin secretion was significantly increased only after the higher calcium doses.--Serum insulin in peripheral venous blood venous blood was unchanged after duodenal application of 20 ml 270 mval/l calcium (n = 5). From these data one has to conclude that the Ca++-content of bile has no stimulatory effect on the exocrine pancreas and on serum gastrin and insulin.

The prostaglandins system and insulin release. Studies with the isolated perfused rat pancreas

Using the isolated perfused rat pancreas PGE2 (1 MUM and 10 muM) had no effect on basal or glucose (10 and 20 mM)-induced insulin release (IR). PGF2 alpha stimulated basal IR at 1 muM and inhibited IR at 10 muM. The glucose-induced IR was unaffected by this PG. Furosemide (5 and 10 mM) led to a monophastic IR at low glucose (glu) and to a potentiation of IR at high glu. Only high indomethacin (Indo) (50 microgram/ml) inhibited glu-induced IR. The stimulatory effect of furosemide on IR could not be inhibited by indomethacin. However mepacrine (0.1 mM) abolished the furosemide effect. Also glu-induced IR was inhibited by mepacrine. Acetylsalicylic acid (30 mg/100 ml) had no significant influence on glu-induced IR. These findings provide evidence that phospholipase activation rather than increased PG synthesis might primarily be involved in the secretory process of insulin.

Indications for a brain uptake of labelled vasopressin and ocytocin and the problem of the blood-brain barrier

Fifteen seconds after intracarotid injection of [125J]-lysine vasopressin, [3H]-ocytocin, tritiated water or [3H]-inulin, the distribution of radioactivity in 18 regions of the rat brain and in the anterior pituitary was determined. Comparing the concentration of the different tracers (in % of injected radioactivity per g brain tissue), it is assumed that a small amount of the labelled neurohormones is taken up by the brain, indicating a penetration of the blood-brain barrier and/or an accumulation within the structures of the barrier system.

Sulphydryl requirement for insulin release from the perfused pancreas. Studies with ethacrynic acid and dithiothreitol

Using the isolated, perfused rat pancreas the importance of sulphydryl groups for the secretory process of insulin was investigated. It was found that ethacrynic acid (EA, 0.075-0.6 mmol/1) caused a dose-dependent, monophasic insulin release. Addition of EA to a glucose-stimulated (20 mmol/1) pancreas led to a sudden increase in hormone release, followed by a dose-dependent inhibition of release, which was not reversible after removal of EA. The same phenomenon was seen in the presence of 20 mmol/1 leucine. Dithiothreitol (DTT, 0.1 and 1 mmol/1) had no effect on basal insulin secretion. Added to a glucose-stimulated pancreas DTT (1 mmol/1) caused a reversible inhibition of insulin release. The persistent inhibitory action of EA on glucose-induced insulin release could be reversed by simultaneous perfusion of EA and DTT. Sequential exposure of a glucose-stimulated pancreas to EA and DTT led to a rapid release of insulin, due to DTT; however, the EA-induced inhibition of insulin secretion could not be prevented. Two kinds of thiol groups in the plasma membrane and in the beta cell might be responsible for the various kinetics of insulin release induced by EA and DTT.

Regional net uptake of 14C-glucose by rat brain under the influence of corticosterone

Fifteen seconds after intracarotid injection of either 14C-glucose or tritiated water in adrenalectomized rats, the net uptake of the respective tracer by 18 brain regions and by the anterior pituitary was measured. Corticosterone added to the injection solution (1 or 100 micrograms ml-1; 0.2 ml per animal) caused a dose-dependent decrease of net uptake of 14C-glucose in twelve regions. Compared to the net uptake of tritiated water which was used as a measure of relative blood flow, it suggests that this effect, at least partially, is due to a decreased blood-brain barrier permeability to 14C-glucose. Furthermore, the regional net uptake of 14C-glucose was estimated in rats with different endogenous corticosterone levels but injected with an identical solution in each case. Statistically significant differences could be observed between adrenalectomized and restrained animals in three brain regions.

[Clinical aspects, diagnosis and treatment of organic hyperinsulinism. Experience with 46 operated patients (author's transl)]

The clinical picture of organic hyperinsulinism is presented with reference to experience in 46 operated patients. For the recognition of disease, a careful history is a decisive contribution. The hunger test showed a characteristic hypoglycemic reaction in 100%; the tolbutamide test gave a positive result in 92%. Insulinomas could be localized angiographically in 71%; in one patient this could only be done with an ERCT. The treatment of choice is operation as soon as possible. If possible, enucleation is to be given preference over pancreas resection because of the low complication rate. A search for ectopic (2%) and multiple (12%) adenomas is important. A cure was achieved in 76% of all those operated on. The hospital mortality was about 4%.

Treatment of patients with prolactinomas

Fifty-one female patients with prolactin producing tumors (PRL 1100 to 88,000 microU/ml) and 26 male patients with prolactin producing tumors (PRL 6500 to 400,000 microU/ml) were studied. Only 25% of the females had visual field defects which were present in 70% of the males. All females had amenorrhea but only 35 had galactorrhea. Hypopituitarism was rarely seen in the females but in most of the male patients. Twenty-four females and all male patients were operated (transphenoidal or transfrontal operation). PRL normalized in only eight females and in none of the males. Two patients became pregnant postoperatively, four after postoperative treatment with bromocriptine. Bromocriptine induced regular menses in 4 other patients operated by transsphenoidal route. Eight patients with microadenoma (PRL less than 4000 microU/ml) were treated with bromocriptine alone of whom two became pregnant. The males were also treated with bromocriptine leading to a significant fall of the PRL level accompanied by improvement of libido, sexual potency and headache. Two patients received radiation postoperatively, which led to a fall of PRL and improvement of visual fields. Since PRL levels remained low after withdrawal of bromocriptine for several months an antiproliferative effect of this drug is suggested. Thus differential therapy of PRL producing tumors is possible: In females selective neurosurgery can alone or combined with medical therapy normalize PRL secretion and ovarian function. In patients with microadenoma bromocriptine alone can be successful. In patients with inoperable large tumors radiation should be advocated. Additional bromocriptine therapy may be helpful to stop tumor growth and alleviate the effects of hyperprolactinemia.