Potent action of leumorphin on consummatory behaviors in rats: comparison with other opioid peptides

Leumorphin is a 29-amino-acid peptide derived from preproenkephalin B. Intracerebroventricular (i.c.v.) injection of leumorphin through an implanted cannula into the lateral ventricle of rats dose-dependently inhibited water intake induced by water deprivation, angiotensin II (AII) and carbachol. This effect was partially reversed by intraperitoneal injection of naloxone, an opiate antagonist. Naloxone alone rather attenuated water intake. The antidipsogenic effect of leumorphin was very potent: 0.6 pmol of the peptide significantly inhibited AII-induced drinking. Dynorphin 1-17 was almost as potent as leumorphin in inhibiting drinking, whereas alpha-neo-endorphin and leucine-enkephalin (Leu-enkephalin) were far less effective. Leumorphin given i.c.v. dose-dependently enhanced eating and this effect was abolished by naloxone. Dynorphin was as potent as leumorphin in inducing feeding, whereas alpha-neo-endorphin and Leu-enkephalin had no significant activity when 6 nmol was used. General activity measured by an Automex was enhanced by i.c.v. injection of leumorphin but required larger amounts of the peptide than did drinking behavior. The very potent and specific effects of leumorphin and dynorphin on drinking behavior suggest that the antidipsogenic activity of these peptides is of physiological significance like their effect on feeding.

Systemic lupus erythematosus sera antilymphocyte reactivity: detection of antibodies to Tac-antigen positive T cell lines

Sera obtained from patients with systemic lupus erythematosus (SLE) were tested for their reactivity to cell lines derived from cutaneous T-cell lymphoma (CTCL), or adult T cell leukaemia (ATL), and with other cell lines, by indirect immunofluorescence method. Approximately one half of SLE sera reacted with the surface antigens of HUT-102 cells, a cell line from CTCL, which constitutively expresses Tac antigen. The titre tended to be higher in the active than in the inactive stage. These positive sera also reacted with other neoplastic or normal T cell lines having Tac antigen. SLE sera reacting with HUT-102 surface antigens were further examined for their reactivities to Tac antigen, the putative IL-2 receptor, using HUT-102 or ATL-2. Pretreatment with anti-Tac monoclonal antibody partially blocked the reactivities to HUT-102 surface antigens in nine of 15 SLE sera tested. The binding of 125I-labelled anti-Tac monoclonal antibody was displaced by the addition of sera from six of 15 SLE patients. In addition, nine of the 15 SLE sera could inhibit the binding of 125I-labelled IL-2 to ATL-2 cells. These results suggested that some of SLE sera contained antibodies against the IL-2 receptor.

A case of adiposis dolorosa: lipid metabolism and hormone secretion

The present report describes a 53-year-old non-obese man with adiposis dolorosa whose pain was dramatically relieved by the intravenous injection of lidocaine. The patient showed a paradoxical response of growth hormone to thyrotropin-releasing hormone. In addition, in-vitro studies on adipose tissue metabolism revealed the reduced glucose conversion to neutral glycerides in painful adipose tissue. These abnormalities may be related in some ways to the pathogenesis of this disorder.

Involvement of peptide histidine isoleucine (PHI) in prolactin secretion induced by serotonin in rats

The possible role of hypothalamic peptide histidine isoleucine (PHI) in prolactin (PRL) secretion induced by serotoninergic mechanisms was investigated in male rats using a passive immunization technique. Intracerebroventricular injection of serotonin (5HT, 10 micrograms/rat) raised plasma PRL levels both in urethane-anesthetized rats and in conscious rats pretreated with normal rabbit serum (0.5 ml/rat, iv, 30 min before). Plasma PRL responses to 5HT were blunted in these animals when they were pretreated with rabbit antiserum specific for PHI (0.5 ml/rat, iv, 30 min before) (mean +/- SE peak plasma PRL: anesthetized rats 271.3 +/- 38.3 ng/ml vs 150.0 +/- 12.6 ng/ml, p less than 0.01, conscious rats 54.3 +/- 6.8 ng/ml vs 30.7 +/- 4.1 ng/ml, p less than 0.025). These results suggest that hypothalamic PHI is involved, at least in part, in PRL secretion induced by central serotoninergic stimulation in the rat.

Osteopenia and circulating levels of vitamin D metabolites in diabetes mellitus

The degree of diabetic osteopenia and serum vitamin D metabolite levels were measured in 14 type 1 (insulin-dependent) and 168 type 2 (non-insulin-dependent) diabetic patients. Based on six indices obtained by microdensitometry, we found the bone mass in 28.6% of type 1 and 26.2% of type 2 diabetic patients to be decreased and in 14.3% and 11.9%, respectively, the decrease was severe. Our method of analysis of bone mass has shown that diabetic osteopenia differs from typical osteoporosis in character. In addition, serum 24,25-dihydroxyvitamin D was significantly decreased both in type 1 and in type 2 diabetes (p less than 0.01), but 1,25-dihydroxyvitamin D was significantly decreased only in type 1 diabetes (p less than 0.01) compared to the controls, being lower than that in type 2 diabetes (p less than 0.05). On the other hand, 25-hydroxyvitamin D was similar to that of the controls, in both types of diabetes.

Distribution of human leumorphin-like immunoreactivity in the monkey spinal cord revealed by immunocytochemistry

The regional distribution of human leumorphin (HL)-like immunoreactivity (HL-LI) in monkey (Macaca fuscata) spinal cord and dorsal root ganglia was investigated by peroxidase-anti-peroxidase immunocytochemistry using specific antiserum. HL-LI-positive fibers and terminals were distributed densely in laminae (Rexed) I and II, and sparsely in laminae III-VII and X, but no immunoreactive elements were observed in the ventral horn, the white matter or the dorsal root ganglia. Many immunoreactive neuronal perikarya were found in laminae I and II. Intrathecal injection of colchicine also revealed the presence of immunoreactive neuronal perikarya in laminae III-VII and X. These results suggest the presence of HL-LI, which represents HL and/or its C-terminal fragment, in the neuronal elements of the monkey spinal cord.

Endogenous opioids and related peptides: from molecular biology to clinical medicine. The Sir Henry Dale lecture for 1985

Advances in techniques in molecular biology have facilitated the research into endogenous opioids and related peptides in several ways. The organization and expression of genes and the primary structure of three precursor proteins of opioid peptides have been elucidated. These studies predicted the presence of potentially bioactive peptides, which has been confirmed by later studies. Advances in techniques in protein chemistry have helped to elucidate the distribution and molecular forms of endogenous opioids and related peptides in the body, and the processing of precursor proteins. Studies on the function of these peptides have shown a broad spectrum of actions. Leumorphin, a newly identified peptide, has been shown to exhibit unique biological activities. In spite of extensive studies, the physiological and pathophysiological significance of opioid peptide systems are not yet completely understood. This is mainly due to the paucity of our knowledge about opioid receptors. Further studies on the subtypes of opioid receptors will help to elucidate all aspects of the function of endogenous opioids and related peptides.

Atrial natriuretic polypeptide: topographical distribution in the rat brain by radioimmunoassay and immunohistochemistry

The widespread distribution of neurons containing alpha-atrial natriuretic polypeptide-like immunoreactivity in the rat brain was demonstrated using radioimmunoassay and immunohistochemistry in conjunction with specific antisera. The highest concentrations of alpha-atrial natriuretic polypeptide-like immunoreactivity were in the hypothalamus and septum, with low but still appreciable concentrations in the mesencephalon, cerebral cortex, olfactory bulb and thalamus by radioimmunoassay. Immunohistochemical studies clearly showed that the perikarya of immunoreactive neurons are most prevalent in the ventral part of the lateral septal nucleus, periventricular preoptic nucleus, bed nucleus of the stria terminalis, periventricular and dorsal parts of the paraventricular hypothalamic nucleus, ventromedial nucleus, dorsomedial nucleus, arcuate nucleus, median mamillary nucleus, supramamillary nucleus, zona incerta, medial habenular nucleus and the periaqueductal grey matter. Scattered neurons were seen in the cingulate cortex, endopiriform nucleus, lateral hypothalamic area, and pretectal and dorsal thalamic areas. In addition to the areas mentioned above, high concentrations of immunoreactive varicose fibers were seen in the glomerular layer of the olfactory bulb, external layer of the median eminence, central to paramedian parts of the interpeduncular nucleus and the paraventricular hypothalamic nucleus. The globus pallidus, medial and central amygdaloid nuclei, dorsal raphe, dorsal parabrachial nucleus, locus coeruleus, vagal dorsal motor nucleus, solitary nucleus and some circumventricular organs, including the subfornical organ and organum vasculosum laminae terminalis, contained considerable numbers of immunoreactive varicose fibers. In dehydrated rats and homozygous Brattleboro rats, the pattern of alpha-atrial natriuretic polypeptide-immunoreactive neurons and varicose fibers was qualitatively similar to that seen in normal conditioned rats. This study gives an atlas of the distribution of the alpha-atrial natriuretic polypeptide-containing neuronal system in the rat brain and provides the groundwork for studying the influence of this new peptide on various brain functions.

ACTH and related peptides: molecular biology, biochemistry and regulation of secretion

The precursor of ACTH and beta-LPH is a glycoprotein with a molecular weight of more than 30 000. Its gene consists of three exons with two intervening sequences and most of the protein coding sequence is in exon 3. The gene is expressed not only in the pituitary gland but also in extrapituitary tissues. The gene expression in the anterior pituitary gland is regulated by CRF and glucocorticoids, but it is regulated differently in other tissues. The processing of the ACTH/beta-LPH precursor yields several peptides, but final products vary in tissues due to differential processing. The processing is abnormal in ACTH-producing tumours, especially in ectopic ACTH-producing tumours. Some abnormalities may also occur at the transcriptional or post-transcriptional level as well. Peptides derived from the same precursor are secreted concomitantly from the pituitary gland. CRF is the major stimulating factor, but vasopressin and some other factors are also involved in stimulating ACTH release. On the other hand, glucocorticoids inhibit ACTH release by acting at the hypothalamic and pituitary levels. In the pituitary ACTH-producing adenomas of Cushing's disease, CRF, vasopressin as well as other non-physiological factors stimulate ACTH secretion. Such abnormal receptor mechanisms are also seen in ectopic ACTH-producing tumours.

Cloning and sequence analysis of cDNA for rat corticotropin-releasing factor precursor

DNA complementary to the rat hypothalamic mRNA coding for the corticotropin-releasing factor precursor (prepro-CRF) has been cloned by screening a cDNA library with a human genomic DNA probe. Nucleotide sequence analysis of the cloned cDNA has revealed that rat prepro-CRF consists of 187 amino acid residues including a putative signal peptide. The CRF and putative signal peptide regions are more highly conserved among rat, human and ovine prepro-CRF than is the cryptic portion.

Specific binding activities and cyclic GMP responses by atrial natriuretic polypeptide in kidney epithelial cell line (LLC-PK1)

Receptor binding activities and cyclic GMP responses by alpha-human atrial natriuretic polypeptide (alpha-hANP) and its fragments were studied in a kidney epithelial cell line (LLC-PK1). Binding of 125I-alpha-hANP to the cells at 0 degrees C was saturable, time-dependent and reversible, indicating the presence of a single class of binding sites. alpha-hANP (7-23)NH2 fragment inhibited most effectively the specific binding of 125I-alpha-hANP to the LLC-PK1 cells, followed by alpha-hANP (17-28) and alpha-hANP (8-22), while alpha-hANP (1-6) and alpha-hANP (24-28) did not. alpha-hANP stimulated the formation of cyclic GMP in the LLC-PK1 cells dose-dependently. Although no fragments of alpha-hANP used were effective for cyclic GMP formation in the LLC-PK1 cells, alpha-hANP (7-23) NH2 antagonized the action of alpha-hANP on cyclic GMP formation. These data suggest that the LLC-PK1 cells retain specific receptors for atrial natriuretic polypeptide (ANP) and respond to ANP by stimulating cyclic GMP formation, and therefore this cell line may be useful for studying the mechanism of action for ANP in renal tubular cells.

Effects of adrenalectomy and dexamethasone administration on the level of prepro-corticotropin-releasing factor messenger ribonucleic acid (mRNA) in the hypothalamus and adrenocorticotropin/beta-lipotropin precursor mRNA in the pituitary in rats

RNA blot hybridization analysis with cloned rat CRF precursor (prepro-CRF) cDNA as a probe showed that prepro-CRF mRNA existed in rat hypothalamic and extrahypothalamic brain tissue, whereas it was undetectable in the pituitary and adrenal. To study the effect of glucocorticoid on the level of prepro-CRF mRNA in the hypothalmus and that of ACTH/beta-lipotropin (beta LPH) precursor mRNA in the pituitary, effects of adrenalectomy and dexamethasone administration were studied in rats. Adrenalectomy markedly raised mRNA coding for ACTH/beta LPH precursor in the anterior pituitary, but not in the neurointermediate pituitary lobe. Hypothalamic pre-pro-CRF mRNA increased only to 152% of the control value, 7 days after adrenalectomy. The administration of dexamethasone (200 micrograms/day for 7 days) started immediately after adrenalectomy lowered the ACTH/beta LPH precursor mRNA level in the anterior pituitary to 19% of the intact control value, whereas the level of prepro-CRF mRNA in the hypothalamus decreased only to 102%. These results suggest that glucocorticoids exert their feedback effect at the level of gene expression on both hypothalamic CRF neurons and pituitary corticotropes. Although the possibility that CRF neurons insensitive to glucocorticoid in the hypothalamus might blunt the change in the prepro-CRF mRNA could not be ruled out, it is also possible that the effect of glucocorticoids on the pituitary is dominant.

Effect of bromocriptine on serum TSH in euthyroid patients with endocrine disorders

In 10 euthyroid subjects a single 2.5 mg per os dose of bromocriptine caused rapid and remarkable decreases in serum TSH. As much as a 0.85 +/- 0.18 (s.d.) microU/ml decrease from the basal level (56 +/- 9%) was observed at 5 hours. A good correlation was observed between the basal TSH level and the TSH decrease after bromocriptine (r = 0.786). In 4 patients taking 5 to 15 mg bromocriptine daily (chronic administration group), another 2.5 mg bromocriptine also caused significant decreases in serum TSH, but the degree (0.42 +/- 0.03 microU/ml, 43 +/- 26% of basal) and duration (maximal at 4 hours) were less than those observed in the untreated group. The lowest TSH levels in these two groups did not differ significantly (0.80 +/- 0.45 and 0.78 +/- 0.53 microU/ml, respectively). The TSH decrease after bromocriptine in the untreated group was found not to correlate significantly with TRH induced TSH increase (r = 0.300). TRH induced TSH increase in the chronic administration group was similar to or greater than that of control subjects with matched basal TSH. The TSH lowering effects of per os prednisolone and triiodothyronine were also studied. Prednisolone exerted a quite similar effect to bromocriptine, but a certain time lag was observed in the case of triiodothyronine. A single dose of bromocriptine was found to lower serum TSH levels even in euthyroid subjects. The effect was considered to be independent of TRH-TSH regulation and to act directly on the TSH release.

Pressor activity of angiotensin II-(2-7)-hexapeptide in man

Pressor activity and speed of metabolic degradation of angiotensin II-(2-7)-hexapeptide [ANG-(2-7)] were studied in 5 normal men. When infused iv at a rate of 72 nmol/kg X min for 7 min, ANG-(2-7) caused a very slight but statistically significant increase in blood pressure. Average blood pressure increases at 2, 5 and 7 min were 5/4, 8/10 and 8/9 mmHg, respectively, and the duration of the pressor action after the cessation of the infusion (T) was 5 min on the average. The pressor activity and T of this peptide were much less than or shorter than those of angiotensin II-(1-7)-heptapeptide [ANG-(1-7)] infused previously in the same 5 normal men at a rate of 18 nmol/kg X min, indicating that the pressor activity ratio of both the peptides in man is 1: greater than 7.2 which is similar to that of angiotensin II-(2-8)-heptapeptide (angiotensin III) and Ile5-angiotensin II (Ile5-ANG II) (1: greater than 5) and that the removal of N-terminal aspartic acid from ANG-(1-7) hastens the speed of metabolic degradation of the peptide as from Ile5-ANG II.

Agonistic activities of isoleucine8-angiotensin II in man

In order to clarify the importance of C-terminal phenylalanine in angiotensin II (ANG II) molecule, agonistic activities of a C-terminal substituted peptide, isoleucine8-angiotensin II (Ile8-ANG II), were studied in comparison with those of sarcosine1-, isoleucine8-angiotensin II (Sar1-, Ile8-ANG II) and isoleucine5-angiotensin II (Ile5-ANG II) in 5 normal men. When infused iv at a rate of 600 pmol/kg X min for 30 min, Ile8-ANG II and Sar1-, Ile8-ANG II raised the blood pressure to the same extent (15/15 mmHg on the average), while the average blood pressure increase was 21/21 mmHg after an iv infusion of Ile5-ANG II at a rate of 5 pmol/kg X min for 30 min. Duration of the pressor action after the cessation of each infusion was 50-90, 90-120 and 10-25 min, respectively. In each case plasma renin activity (PRA) decreased and plasma aldosterone (PA) increased. When infused iv at a rate of 10 pmol/kg X min (maximum non-pressor dose) for 120 min, both Ile8-ANG II and Sar1-, Ile8-ANG II lowered PRA and increased PA gradually, but 100 mg oral captopril given immediately before these infusions caused no significant increase in PRA or no significant decrease in PA but again a decrease in PRA and an increase in PA.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation by leumorphin of prolactin secretion from the pituitary in rats

The effect of leumorphin (LM), one of big leu-enkephalins derived from preproenkephalin B, on PRL secretion was studied in the rat in vivo and in vitro. Intracerebroventricular injection of synthetic porcine LM (0.06-6 nmol/rat) caused a dose-related increase in plasma PRL levels in urethane-anesthetized male rats and in conscious freely moving rats. Intravenous injection of LM (3 nmol/100 g BW) also raised plasma PRL levels in these animals. The plasma PRL response to intracerebroventricular LM (0.6 nmol/rat) was blunted by naloxone (125 micrograms/100 g BW, iv). The stimulating effect of LM on PRL release was the most potent among the peptides derived from preproenkephalin B. In in vitro studies, PRL release from superfused anterior pituitary cells was stimulated in a dose-related manner by LM (10(-9)-10(-6) M), and the effect was blunted by naloxone (10(-5) M). These results suggest that LM has a potent stimulating effect on PRL secretion from the pituitary in the rat by acting, at least in part, directly at the pituitary through an opiate receptor.

Diabetic osteopenia and circulating levels of vitamin D metabolites in type 2 (noninsulin-dependent) diabetes

The degree of diabetic osteopenia and serum vitamin D metabolite levels were measured in 168 type 2 (noninsulin-dependent) diabetic patients. Based on six indices obtained by microdensitometry, we found the bone mass in 26.2% of diabetic patients to be clearly decreased and in 11.9% to be severely decreased. Our direct method of analysis of bone mass shows that diabetic osteopenia differs from typical osteoporosis in character. In addition, serum 24,25-dihydroxyvitamin D was significantly decreased (P less than 0.01), but 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D were similar to those of controls.

Vagal modulation of arginine- and glucagon-induced pancreatic somatostatin secretion

In order to elucidate the role of the vagus nerve in the regulation of pancreatic somatostatin secretion, the effect of electrical stimulation of the vagus on the isolated perfused rat pancreas was studied. Somatostatin release induced by 19 mM arginine in the presence of 11 mM glucose or 10(-6)M glucagon in the presence of 5.5 mM glucose was suppressed by vagal stimulation. This suppressive effect on somatostatin was eliminated in the presence of 10(-5)M atropine plus glucagon, while somatostatin release was significantly enhanced in the presence of atropine plus arginine. We conclude that pancreatic somatostatin secretion may be regulated not only by a cholinergic inhibitory neuron but also by a stimulatory non-cholinergic neuron.

Involvement of growth hormone-releasing factor in growth hormone secretion induced by gamma-aminobutyric acid in conscious rats

Intracerebroventricular (icv) injection of gamma-aminobutyric acid (GABA) (10 mumol/rat) resulted in an increase in plasma GH in conscious freely moving rats pretreated with normal rabbit serum (0.5 ml/rat, iv). Rabbit antiserum specific for rat GH-releasing factor (GRF) (0.5 ml/rat, iv) abolished GH release induced by GABA in these animals. Rabbit anti-rat GRF serum also blunted GH release induced by a Met5-enkephalin analog, FK33-824 (10 micrograms/100 g BW, iv) in conscious rats. Considering our previous findings that rat GH release induced by FK33-824 was blunted by GABA antagonists (Endocrinology 103:1033, 1981), these results suggest that GH secretion induced by opioid peptides via GABAergic mechanisms is mediated, at least in part, by hypothalamic GRF in the rat.