In mice aggressive behavior provokes vast increase in plasma renin concentration, causing only slight, if any, increase in blood pressure

Liver injury after an aggressive encounter in male mice

Acute and intense psychological stressors induce cell damage in several organs, including the heart and the liver. Much less is known about social stress. In male mice, aggressive behavior is the most common social stressor. It is remarkable that upon fighting, submandibular salivary glands release a number of peptides into the bloodstream including epidermal growth factor (EGF). We showed previously that released EGF protects the heart from cell damage in this particular stressful situation. Here, we studied the effect of an aggressive encounter on the liver and whether EGF has a similar effect on this organ. An aggressive encounter in male mice caused inflammatory response and a transient increase in plasma alanine and aspartate transaminase activities. At 3 h, focal infiltration of neutrophils was observed in liver parenchyma. These cells accumulate on eosinophilic hepatocytes, which may correspond to dying cells. A few hours later, evidence of necrotic lesion was observed. Surgical excision of submandibular glands, sialoadenectomy, did not prevent the rise in plasma EGF concentration and did not affect the increase in plasma transaminase activities. Neither did the administration of tyrphostin AG-1478 (inhibitor of EGF receptor kinase) alter the increase in plasma alanine transaminase activity. However, it did enhance the rise in both aspartate transaminase and creatine kinase activity, suggesting heart damage. We conclude that an aggressive encounter causes mild liver damage and that released EGF does not protect this organ, in contrast to its effect on the heart.

Psychosocial vs. "physical" stress situations in rodents and humans: role of neurotrophins

Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are well-studied polypeptide growth factors involved in the development and maintenance of specific peripheral and central populations of neuronal cells. In addition to its role as a neurotrophic agent, NGF controls very complex functions in vertebrate physiology. A variety of cells outside the nervous system are in fact able to synthesize NGF including epithelial cells, fibroblasts, lymphocytes, and macrophages. NGF target cells have been identified in the nervous, immune, and endocrine systems, suggesting that NGF may operate through multiple paths to ultimately regulate physiological homeostasis and behavioral coping. We used a mouse model of social stress to demonstrate that NGF levels increase both in plasma and in the hypothalamus following intermale aggressive interactions. The investigation has been extended to other species, including humans, to show that labour, lactation, and the anticipation of the first jump with a parachute also result in increased NGF plasma levels and in changes in the distribution of NGF receptors on lymphocytes. BDNF activation is caused by both physical and social stress events. The aim of this review is to (1) outline the current understanding of the roles of NGF and BDNF in stress-related physiological changes in vertebrates, in particular for physical vs. psychological stressors, which may activate both similar and different neurobiological pathways, and (2) summarize recent efforts to derive pharmacological strategies from the increasing body of BDNF and NGF neurobehavioral data.

Angiotensin II promotes atherosclerotic lesions and aneurysms in apolipoprotein E-deficient mice

Increased plasma concentrations of angiotension II (Ang II) have been implicated in atherogenesis. To examine this relationship directly, we infused Ang II or vehicle for 1 month via osmotic minipumps into mature apoE(-/-) mice. These doses of Ang II did not alter arterial blood pressure, body weight, serum cholesterol concentrations, or distribution of lipoprotein cholesterol. However, Ang II infusions promoted an increased severity of aortic atherosclerotic lesions. These Ang II-induced lesions were predominantly lipid-laden macrophages and lymphocytes; moreover, Ang II promoted a marked increase in the number of macrophages present in the adventitial tissue underlying lesions. Unexpectedly, pronounced abdominal aortic aneurysms were present in apoE(-/-) mice infused with Ang II. Sequential sectioning of aneurysmal abdominal aorta revealed two major characteristics: an intact artery that is surrounded by a large remodeled adventitia, and a medial break with pronounced dilation and more modestly remodeled adventitial tissue. Although no atherosclerotic lesions were visible at the medial break point, the presence of hyperlipidemia was required because infusions of Ang II into apoE(+/+) mice failed to generate aneurysms. These results demonstrate that increased plasma concentrations of Ang II have profound and rapid effects on vascular pathology when combined with hyperlipidemia, in the absence of hemodynamic influences.

Rodent submandibular gland peptide hormones and other biologically active peptides

The cervical sympathetic trunk-submandibular gland neuroendocrine axis plays an integral role in physiological adaptations and contributes to the maintenance of systemic homeostasis, particularly under the 'stress conditions' seen with tissue damage, inflammation, and aggressive behavior. The variety of polypeptides, whose release from acinar and ductal cells is under sympathetic nervous system control, offers coordinated and progressive levels of endocrine communication. Proteolytic enzymes (e.g. the kallikreins and furin maturases) are involved in the conversion of inactive precursors (e. g. Pro-EGF and SMR1) into biologically active molecules (e.g. EGF, SMR1-pentapeptide), which act on local or distant targets and thereby modulate the homeostatic process.

Acinar cells are target cells for androgens in mouse submandibular glands

The variable coding sequence (VCS) multigene family encodes diverse salivary proteins, such as the SMR1 prohormone and the PR-VB1 proline-rich protein in the rat. In situ hybridization was used to study the cell-specific expression of two new mouse VCS genes, Vcs1 and Vcs2. We show that the Vcs1 transcripts, which code for a proline-rich protein, MSG1, are highly abundant in male and female parotid glands, in which they are specifically detected in acinar cells. No expression was seen in the submandibular or sublingual glands. In contrast, Vcs2 transcripts were found only in the acinar cells of the submandibular glands (SMGs) of male mice, in which they are expressed in response to androgens. Expression was found to be heterogeneous within acinar structures. No Vcs2 transcripts were detected in the SMGs of females or castrated males by Northern blot, RNase protection, or in situ hybridization. Androgen administration to females or castrated males induced expression at a level comparable to that of intact males. The Vcs2 gene is the first example of a mouse androgen-regulated gene that is expressed in SMG acinar cells. This result, in addition to our previous observation on SMR1 expression in rats, demonstrates that both acinar cells and granular convoluted tubule (GCT) cells are target cells for androgen action in rodent SMG.

Targets for SMR1-pentapeptide suggest a link between the circulating peptide and mineral transport

The submandibular rat 1 protein (SMR1) is selectively processed at pairs of basic amino acid residues in a tissue- and sex-specific manner. We have mapped peripheral targets for the final secretory maturation product of SMR1, the pentapeptide QHNPR, by examining in vivo the tissue distribution of the radiolabeled peptide using beta-radio imager whole body autoradiography. The characteristics of tissue uptake allowed specific binding sites at physiological peptide concentrations to be identified within the renal outer medulla, bone and dental tissue, glandular gastric mucosa, and pancreatic lobules. Direct evidence that pentapeptide binding sites are localized in selective portions of the male rat nephron, within the S3, S2, and S1 segments of the proximal tubules, was obtained. In bone tissue the pentapeptide exclusively accumulates within the trabecular bone remodeling unit, and in dental tissue it concentrates within the tubules of the dentinal rat incisor. In relation to male rat-specific behavioral characteristics, our data suggest that the circulating androgen-regulated SMR1-derived pentapeptide is primarily involved in the modulation of mineral balance between at least four systems: kidney, bone, tooth, and circulation.

NGF regulatory role in stress and coping of rodents and humans

Nerve growth factor (NGF) is a polypeptide growth factor which exerts trophic and differentiative effects on specific peripheral and central populations of neurons. Recent data showing that various cellular types of the endocrine and immune systems are able to synthesize and release NGF have suggested that this neurotrophic factor may also play an important role in vertebrate physiologic homeostasis. Previous studies using a mouse model of aggressive behavior have shown that NGF levels increase in both plasma and the CNS following intermale agonistic encounters. More recently, we have extended this research area to include other species: in particular, humans. The data now available indicate that labour and lactation, or the occurrence of a stressful event such as the very first jump with a parachute causes in NGF plasma levels as well as changes in the distribution of NGF receptors on lymphocytes. This review aimed to outline the current understanding of NGF role in vertebrates in stress-related events.

Evidence of a role for nerve growth factor in the effect of sialoadenectomy on body temperature of parasite-infected mice

Mice infected with Schistosoma mansoni were used to investigate the role of the submaxillary salivary gland and nerve growth factor (NGF) in temperature response. The results showed that the infection increased (36.5 +/- 0.3 vs 35.7 +/- 0.2), while sialoadenectomy decreased (34.4 +/- 0.2 vs 35.1 +/- 0.2) body temperature. These temperature changes were associated with high or low circulating NGF levels, respectively. It was also found that infection altered the distribution of oxytocin-positive neurones in the hypothalamus and that administration of 20 mu g of purified NGF in normal mice raised (36.1 +/- 0.2 vs 35.1 +/- 0.2) and of NGF antibodies decreased (34.0 +/- 0.2 vs 35.1 +/- 0.2) body temperature. Taken together, these observations suggest that salivary NGF influences the temperature set-point in adult rodents, but the mechanism regulating these events remains to be elucidated.

Three novel SMR1-related cDNAs characterized in the submaxillary gland of mice show extensive evolutionary divergence in the protein coding region

We have previously characterized an abundant male-specific mRNA from the submaxillary gland (SMG) of rats, encoding the SMR1 (androgen-regulated) protein, which has the structure of a prohormone and is processed by maturation enzymes to release a small peptide in the blood and saliva. We have now characterized three SMR1-related cDNAs in the SMG of Balb/c mice. These cDNAs encode three novel proteins, designated MSG1, MSG2 and MSG3. They are 639, 662 and 471 nucleotides (nt) long, respectively, and the corresponding mRNAs appear to be expressed only in the SMG. The putative polypeptides they encode carry an N-terminal secretory peptide sequence and are, therefore, presumably secreted into saliva. Although closely related, the three mRNAs show striking differences: a particularly different expression pattern and an extremely high degree of variability observed in the central part of the molecules. The MSG1 and MSG3 cDNAs are identical, except for a 173-bp insert found only in MSG1. This insert contains three Pro-rich repeats (GPGIGRPPPPPP), reminiscent of the most abundant multigenic family of the SMG, the Pro-rich proteins (PRP). Although MSG1 shares several common features with PRP, it is structurally related to SMR1. The unusually high ratio of replacement/silent nt changes provides a basis to address complex aspects concerning the molecular events leading to the emergence of new proteins in the SMG.

Selective processing of submandibular rat 1 protein at dibasic cleavage sites. Salivary and bloodstream secretion products

The amino acid sequence of submandibular rat 1 (SMR1) protein, deduced from its cDNA sequence, led to the prediction that the SMR1 gene encodes a hormone-like precursor [Rosinski-Chupin, I., Tronik, D. & Rougeon, F. (1988) Proc. Natl Acad. Sci. USA 85, 8553-8557]. SMR1 contains an N-terminal putative secretory signal sequence and a tetrapeptide (QHNP), located between dibasic amino acids which constitute the most common signal for prohormone processing. We have isolated and characterized from the male rat submandibular gland and its secretions three structurally related peptides, namely an undecapeptide (VRGPRRQHNPR), a hexapeptide (RQHNPR) and a pentapeptide (QHNPR) generated from SMR1 by selective proteolytic cleavages at pairs of arginine residues. The biosynthesis of these peptides is subjected to distinct regulatory pathways depending on the organ, sex and age of the rat. Furthermore, the peptides are differentially distributed in the submandibular gland and in resting or epinephrine-elicited submandibular salivary secretions, suggesting distinct proteolytic pathways for their maturation. The undecapeptide is generated in the gland of both male and female rats, but under basal conditions it is only released into the saliva in male animals. The hexapeptide is produced in large amounts in the gland of adult male rats and released into the saliva in both resting and stimulated conditions. The pentapeptide appears only in the male saliva and is present mostly under stimulated conditions. In addition, administration of epinephrine induces the release of the hexapeptide from the submandibular gland into the bloodstream. The evidence indicates that the rat submandibular gland can function as a dual exocrine and endocrine organ for the SMR1-derived hexapeptide, as has been reported for nerve growth factor, epidermal growth factor, renin and kallikrein. Although the biological activities of the SMR1-derived peptides are not yet known, their high production and adrenergic-induced release only into the saliva and bloodstream of adult male rats, suggest a physiological involvement in some male-specific processes.

Removal of the submaxillary salivary glands first increases and then abolishes the agonistic response of male mice in repeated social encounters

Adult male mice of the CD-1 strain were sialectomized (bilateral removal of submaxillary salivary glands) under IP Nembutal anesthesia and then individually housed for 5 weeks. Control mice were sham operated. The behaviors of sialectomized and control mice towards untreated, intact, matched opponents were videotaped during the first 10 min of a 20-min social encounter repeated for 10 consecutive days (isolation days 36-46). On the first session, sialectomized mice exhibited significant increases in elements of aggression (attack, bite, offensive sideways, offensive upright, and tail rattling). These behavioral changes significantly decreased over the remaining encounters, while defensive behaviors (defensive upright, oblique, parry, and defensive sideways) and elements of arrested flight increased progressively. The results suggest that sialectomy, perhaps by removing salivary NGF, interferes with the coping response of mice towards repeated agonist challenge from a conspecific.

The granular convoluted tubule (GCT) cell of rodent submandibular glands

The granular convoluted tubule (GCT) is a segment of the duct system of all rodents, situated between the striated and intercalated ducts. It has the peculiar property of synthesizing a large variety of biologically active polypeptides whose role in saliva remains unknown. The literature on the fine structure of GCT cells is critically reviewed. Some recent developments on endocrine regulation of the structure and contents of rodent GCT cells are summarized, with emphasis on EGF, NGF, renin, and kallikrein proteases. A survey of the distribution of GCT cells in several vertebrate families is presented.

Phenotypic inhibition of the renin-angiotensin system, emergence of the Ren-2 gene, and adaptive radiation of mice

The renin-angiotensin system in sub-genus Mus displays unique features including duplication of the renin gene in most strains, strong expression of the second gene in submandibular gland of males, and inhibited responses to injected renin. Our findings indicate that this inhibition results from a paucity of renin substrate and is consistent with first-order kinetics. We find substrate paucity to be a feature of both sexes and all sub-species and strains of Mus irrespective of gene duplication. Attempts to increase the level of substrate in blood by intravenous injection caused marked increases in blood pressure in Mus, suggesting that substrate paucity was a phenotypic prerequisite for successful emergence of enhanced renin expression in salivary gland. We propose that these phenomena are linked to salivary "lethal factor", possibly transferred by biting, in an evolutionary sequence that has provided a major selective advantage for Mus and influenced the ecology and evolution of rodents.

N-linked glycosylation affects the processing of mouse submaxillary gland prorenin in transfected AtT20 cells

Most mouse inbred strains carry two renin genes, Ren-1 and Ren-2, Renin-2, the product of the Ren-2 gene, is highly expressed in the submaxillary gland. It is a renin isoenzyme 96% similar to kidney renin-1, but unglycosylated. In order to investigate if glycosylation of prorenin affects its processing and/or secretion we have introduced two potential N-linked glycosylation sites into preprorenin-2 cDNA using site-directed mutagenesis. Expression plasmids were derived from wild-type and mutant renin-2 cDNA and were transfected into AtT20 cells. Both transfected cells, expressing glycosylated or unglycosylated forms, secreted prorenin and renin by the constitutive and regulated pathways, respectively. Prorenin was correctly processed to active renin but the second maturation site was not cleaved in AtT20 cells. The comparison of glycosylated and unglycosylated renin expression showed a diminished secretion of glycosylated active renin. Prevention of glycosylation with tunicamycin resulted in an improved secretion of active renin. Moreover, the efficiency of the trypsin activation in vitro was reduced for glycosylated prorenin and it was restored when the activation was performed on mutant renin secreted from tunicamycin-treated cells. It is proposed that the bulky carbohydrates attached to prorenin constitute a steric hindrance to proteolysis by maturation enzymes.

Changes of NGF level in mouse hypothalamus following intermale aggressive behaviour: biological and immunohistochemical evidence

Nerve growth factor (NGF) immunoreactivity was detected in the hypothalamus of adult male mice. NGF-immunoreactive cell bodies were examined through consecutive brain sections, and it was found that most of the NGF-positive cells were located in the dorsomedial and mediolateral portions of the hypothalamus. Tissue culture bioassays showed that hypothalamic extract elicits neurite outgrowth from both chick sensory ganglia and rat superior cervical ganglia neurons, and that these effects are inhibited by addition of NGF antibodies. Our results also showed that intermale aggressive behaviour induced by 6-8 weeks of social isolation induces an NGF increase in the hypothalamic area, which is not abolished by sialoadenectomy, suggesting that the increased brain NGF is locally synthesized, and does not come from salivary sources. Likewise, the level of NGF in the hypothalamus of adrenalectomized fighting mice increased, although to a much lesser extent, when compared to hypothalamic levels of sham-operated fighting mice. The present results and a recent report showing that aggressive behaviour causes an increase of mRNANGF in hypothalamic areas are discussed in relation to a possible functional role of NGF in these brain structures.

Aggressive behavior induces release of nerve growth factor from mouse salivary gland into the bloodstream

Intraspecific fighting induced by 6-8 weeks of social isolation results in massive release of nerve growth factor (NGF) into the bloodstream of adult male mice. The amount of circulating NGF is highly correlated with the number of fighting episodes. Biological, radioimmunological, immunohistochemical, and ultrastructural studies show that NGF is discharged from the salivary gland into the blood within minutes after fighting and reaches the highest level 3-4 hr later. Adrenergic innervation of the salivary gland or adrenalectomy does not abolish the NGF release. Corticotropic hormones do not induce NGF increase in the blood. Daily administrations of highly purified NGF (3 micrograms per g of body weight) result in a considerable increase in the volume of adrenal glands. These findings are unequivocable evidence for a physiological role of the mouse salivary glands as a major source of blood NGF.

Aggressive behavior in adult male mice elevates serum nerve growth factor levels

By use of a specific and sensitive beta-nerve growth factor radioimmunoassay (beta NGF-RIA), serum beta NGF concentrations were measured in adult male Swiss-Webster mice under various physiological conditions. Animals killed on the day of arrival from the animal supplier showed wide variations (3-15 ng beta NGF/ml) in serum beta NGF levels. These levels significantly decreased if the animals were maintained under individually housed conditions for at least 6 days prior to death. Aggression caused by social contact between previously individually housed animals raised serum beta NGF levels by two orders of magnitude relative to serum beta NGF concentrations in nonaggressive mice. Testosterone propionate treatment (10 mg/animal) 5 days prior to death did not elevate serum beta NGF levels in individually maintained animals. However, the hormone pretreatment markedly augmented serum beta NGF levels in aggressive mice compared with the levels in hormone-treated nonaggressive animals. Removal of the submandibular-sublingual salivary glands 10 days prior to death completely abolished the increase in serum beta NGF due to aggression. The high serum beta NGF levels, as measured by competitive RIA in aggressive mice, were confirmed by a neurite outgrowth PC-12 bioassay system. In conclusion, serum beta NGF in adult male mice is subject to alteration by environmental stress.

Cyclocytidine-induced release of nerve growth factor from mouse submandibular glands enhances regeneration of sympathetic fibers in adult mice

The injection of a drug endowed with the property of stimulating alpha-adrenergic receptors, cyclocytidine (Cyclo-C), produces drastic depletion of NGF from the granular convoluted tubules (GCT) of the mouse submaxillary salivary gland and a marked NGF level increase in the bloodstream. The NGF discharged from the gland gains access to the blood. Histological studies, immunohistochemistry, in vitro biological assays and radioimmunoassays gave evidence for the growth response elicited by the endogenously released salivary NGF in intact and surgically axotomized sympathetic ganglia. These results suggest that the mouse salivary NGF displays a biological activity on its target sympathetic nerve cells.

Increase in plasma renin in aggressive mice originates from kidneys, submaxillary and other salivary glands, and bites

Aggressive behavior in mice caused a vast release of renin into the plasma. The present data support previous findings that the main sources were the submaxillary gland and kidney. In addition, unidentified salivary glands capable of releasing renin into the saliva were demonstrated by alpha-adrenergic stimulation. The role of these glands in generating plasma renin is unknown. Experiments were performed that strongly support the possibility that aggression-provoked salivary renin may be transferred by bites from one animal to another.

The biochemistry of aggression-provoked renin

The biochemistry of the renin-angiotensin system in aggressive mice may question a simple role of the system in blood pressure regulation. When male mice are fighting, their plasma concentration of active renin may rise several hundred fold without affecting blood pressure. The source of this renin is secretion to the blood from the submaxillary gland and the kidneys, but also small salivary glands may contribute. A further source may be salivary renin transferred by bites from one animal to another, as indicated by recent experiments. The renin concentration in saliva of an aggressor during a fight reaches values of 6000 GU/ml (15 mg/ml). The huge increase in plasma renin is caused by fully enzymatic active 40 000 Mw renin. Preliminary data, collected in order to study whether this renin is active also in vivo, show the following: Inactive renin is present in a small invariable concentration. The renin substrate is consumed in vivo and the measured generation rate of angiotensin is that expected from the renin and substrate concentration. The data seem to indicate that the high concentration of aggression-provoked renin is active in vivo. It is unknown how the mouse protects its blood pressure against this hyperactive pressor system.

High levels of active 40 000-dalton renin in mouse saliva, but no evidence of inactive or high molecular weight forms

The presence of renin in parasympathetically elicited mouse saliva was demonstrated by using both the antibody trapping method, which measures renin's enzymatic activity, and a direct radioimmunoassay, which detects the renin molecule by its antigenic properties. Crossed immunoelectrophoresis of saliva samples using an antiserum elicited against pure submaxillary renin showed only one precipitation line, indicating the presence of only one form of renin. The position of the line was similar to that found when submaxillary gland extract was subjected to crossed immunoelectrophoresis. Tandem crossed immunoelectrophoresis showed complete identity between antigenic determinants in submaxillary and salivary renin. An apparent molecular weight of about 35 000 and 38 000 was found when saliva samples were subjected to gel filtration on Ultrogel AcA 44 and Sephadex G-100, respectively. No high molecular weight forms were present and no inactive forms could be demonstrated after limited pepsin or trypsin proteolysis. The specific enzymatic activity of renin in pilocarpine saliva was 0.37 Goldblatt Units (G.U.) . microgram-1, which is identical to that of pure submaxillary gland renin (0.41 G.U. . microgram-1) and to that to the storage form of renin in the submaxillary gland (0.4 G.U. . microgram-1) An identical Km value was found for salivary renin, 1.01 microM, and for pure submaxillary renin, 0.98 microM. It is concluded that renin in pilocarpine-elicited saliva is similar to the storage form of renin in the submaxillary gland with respect to molecular weight, enzymatic and immunological properties.

Aggressive behavior in mice provokes a marked increase in both plasma epidermal growth factor and renin

The plasma concentration of epidermal growth factor (EGF) in normal, nephrectomized and sialectomized mice is about 0.5 nmol/l. Aggressive behaviour results in a parallel increase in both plasma EGF and plasma renin for both normal and nephrectomized mice. The plasma concentration of EGF increases around 300- and 150-fold respectively; no increase is observed in sialectomized mice, suggesting that the submaxillary gland is an important source of liberated EGF. Virtually all the EGF is found in plasma as a low molecular species that behaves as pure EGF, when examined by radioimmuno- and radioreceptor assays.

Essential hypertension: abnormal renal vascular and endocrine responses to a mild psychological stimulus

We have assessed the influence of a mild emotional stimulus on arterial blood pressure, heart rate, renal blood flow, plasma renin activity (PRA), and plasma aldosterone concentration in 24 normal subjects, eight of who had a parent with hypertension, and in 15 patients with essential hypertension. A nonverbal IQ test, Raven's Progressive Matrices, was employed as the stimulus. In 11 of the 15 hypertensives, arterial blood pressure rose transiently by 7 mm Hg or more, but in only three of 16 normal subjects (x2 = 7.23, p less than 0.01). Transient moderate increases in heart rate were also more common in the hypertensives (p less than 0.01). Renal blood flow rose in 11 of 16 normal subjects and fell in each of the 15 patients with essential hypertension (x2 = 15.1; p less than 0.005). As opposed to the transient changes in arterial pressure and heart rate, the fall in renal perfusion was sustained. The PRA fell in 10 of the 16 normal subjects with a negative family history and rose in 14 of 15 patients with essential hypertension (p less than 0.005). Changes in plasma angiotensin II concentration and in plasma aldosterone were in accord with the changes in PRA, but plasma cortisol did not change. Both the renal vascular response and the change in PRA were intermediate in normal subjects in whom family history was positive for hypertension. For the entire group of 39 subjects there was statistically significant agreement between the direction of the renal vascular response and the directional change in PRA: renal blood flow rose when PRA fell and fell when PRA rose (p less than 0.005). We conclude that there is an abnormality in the control of both the renal circulation and of renin release in patients with essential hypertension in response to psychological provocation, and that a similar process is present in some normotensive subjects whose parents have hypertension.

High-affinity binding of folate to a protein in serum of male subjects

The binding pattern of [3H]folate in the serum of male subjects was studied in equilibrium dialysis experiments (pH 7.4, 37 degrees C). It was possible to distinguish between a high (association constant, Kass = 10(10) (mol/l)-1; maximum binding of folate = 0.6 nmol/l) and a low affinity type of binding. The high-affinity binder was a trace protein (molecular size approximately 35 000) which was eluted with 30 mmol/l NaC, (pH 6.3) from serum subjected to DEAE-Sepharose CL-6B chromatography. The low-affinity binding activity mainly associated with albumin was eluted with 1 mmol/l NaCl. High-affinity binding was depressed at 7 degrees C (Kass = 10(9) (mol/l)-1). Furthermore, methotrexate acted as a weak inhibitor of high-affinity binding, the molar methotrexate/folate ratio being 100/1 at 50% inhibition.

Aggression-provoked renin release from extrarenal and extrasubmaxillary sources in mice

In submaxillary sialoadenectomized and nephrectomized mice aggressive behaviour provoked 5 to 40-fold increases in plasma renin concentration. The changes in renin concentration with time were different in different groups of confronted mice with only partial correlation between the pattern and the observable degree of fight. The changes were similar in sialoadenectomized mice with untouched kidneys as in sialoadenectomized and nephrectomized, indicating that aggression causes no measurable, if any, renal renin release. Repeated aggression with 2 hourly intervals provoked repeated renin release from extrarenal and extrasubmaxillary sources. The renin concentrations of different organs showed the same mutual relationship as in other mammals, but were about 10-fold higher. Splenectomy was without effect on the aggression-provoked renin release. Antibodies against pure mouse renin neutralized the renin in plasma and organs, which contained only insignificant, if any, pepsin activatable inactive renin. Adrenaline, apomorphine, carbachol and dihydralazine were as isoprenaline and noradrenaline without effect on renin release in sialoadenectomized and nephrectomized mice.