Neuronal storage of histamine in the brain and tele-methylimidazoleacetic acid excretion in portocaval shunted rats

Rats with portocaval anastomosis (PCA), an animal model of hepatic encephalopathy (HE), have very high brain histamine concentrations. Our previous studies based on a biochemical approach indicated histamine accumulation in the neuronal compartment. In this study, immunohistochemical evidence is presented which further supports the amine localization in histaminergic neurons. These neurons become pathological in appearance with cisternae frequently seen along histaminergic fibres in many brain areas, including the hypothalamus, amygdala, substantia nigra and cerebral cortex. Such formations were not observed in sham-operated animals. The neuronal deposition is predominant, and unique for histamine. It serves as a mechanism to counterbalance excessive brain neurotransmitter formation evoked by PCA. However, there are other mechanisms. The data provided here show that there is also a significant increase in histamine catabolism in the shunted rats, as reflected by both the higher brain N-tele-methylhistamine (t-MeHA) concentration and urinary excretion of N-tele-methylimidazoleacetic acid (t-MelmAA), a major brain histamine end product. The stomach, in addition to the brain, is a site of enhanced histamine synthesis in portocavally shunted subjects. After gastrectomy or food deprivation to eliminate the contribution of the stomach, shunted rats excrete significantly more t-MelmAA, implying the role of the CNS. This last finding suggests that under strictly defined conditions, namely in parenterally fed HE patients with abnormal plasma L-histidine, the measurement of urinary t-MelmAA might provide valuable information concerning putative brain histaminergic activity.

Liver regeneration attenuates increased voluntary alcohol intake evoked by the liver damage

Liver dysfunction induced in Wistar rats either surgically (by construction of portocaval anastomosis) or chemically (by chronic administration of thioacetamide) led to increased voluntary alcohol intake. Alcohol preference could be attenuated by liver regeneration that was triggered by a two-thirds hepatectomy done on cirrhotic rats. The brain serotonin system was activated in portocaval anastomosis rats and unchanged in thioacetamide-treated rats, thus suggesting that serotonin is not likely to be implicated in the mechanism(s) underlying development of alcohol preference in these rats. Also, tetrahydro-beta-carboline could possibly be excluded from consideration. Neither change in the brain concentration or distribution of tetrahydrobetacarboline after long-term treatment with thioacetamide could be found.

Effect of pargyline on brain N-tele-methylhistamine in portocaval-shunted rats: relation to amine neurotransmitters

HPLC determination of histamine, serotonin, dopamine, and noradrenaline in the brain tissue of rats with portocaval anastomoses (PCA) has revealed a selective increase in histamine concentration. In the posterior hypothalamus, the steady-state level of the amine metabolites showed an inverse pattern; N-tele-methylhistamine (t-MeHA), as estimated by gas chromatography-mass spectrometry, was not changed significantly by portocaval shunting, whereas 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid were more than doubled. Interestingly, the net increase in t-MeHA concentration in response to pargyline (80 mg/kg i.p.) was almost the same for PCA and sham-operated rats. This implies that the great enhancement of the histamine level in this area might be a consequence of the persistent stimulation of its synthesis and the unchanged activity of histaminergic neurons. In the rest of the brain, on the other hand, the steady-state level of t-MeHA was higher after PCA (3.8-fold), as were the levels of 5-HIAA and homovanillic acid. Surprisingly, t-MeHA remained unchanged after monoamine oxidase blockade. Of the pargyline-induced alterations in the concentrations of indoles and catechols, the most pronounced were those in the serotonin level; serotonin was elevated more than twofold in hypothalamus and more than 12-fold in the rest of the brain, with a concomitant 80% decrease in 5-HIAA. The dopamine and, to a much smaller extent, noradrenaline levels were also increased, and the levels of homovanillic acid and 3,4-dihydroxyphenylacetic acid fell below the detection limit. The study suggests that at least two different mechanisms operate in the brains of PCA rats to counteract the excessive synthesis of neuromediators, e.g., increased deposition and increased metabolism.

The FAD dependent amine oxidases in relation to developmental state of enterocyte

Epithelial cells from bovine and guinea pig small intestines contain monoamine and polyamine oxidases with MAO-A preponderance at any maturational stage. For either species, Km values for 5HT and N1acetylspermine remain throughout cellular maturation on the same levels, whereas the Vmax values do not. For serotonin, the dividing crypt cells showed in cow lower and in guinea pig higher Vmax than the mature cells; for N1acetylspermine, mature cells, independently of species, showed lower Vmax.

Histamine: its metabolism and localization in mammary gland

1. Mammary gland of mouse (Mus musculus), rat (Rattus rattus), guinea pig (Cavia porcellus), cow (Bos taurus) and pig (Sus scrofa) contains different but always high concentrations of histamine. 2. Generally, the tissue histamine is localized in mast cells, although non-mast cell histamine immunoreactivity is also present in mammary glands of the mouse, cow and pig. No histamine immunoreactive nerves could be detected. 3. Mammary glands are able to synthesize and inactivate histamine; the activity of specific histidine decarboxylase and at least one of the catabolizing enzyme could be demonstrated. 4. Histamine fulfils basic criteria for being involved in physiological function of mammary glands.

Decreased histamine content and metabolism in mammary cancer tissue from C3H mice

Histamine (HA) level and its metabolism in adenocarcinoma mammae, spontaneously growing cancer in C3H mice, were examined in relation to the type of tumor, intensity of tumor vascularization and the presence or absence of a secretory function. Histamine concentration being in mammary gland one of the highest among mammalian organs (418 nmol/g) was decreased by 90% in tumor (34 nmol/g). Similarly, histidine decarboxylase (HDC) activity dropped from approximately 7.6 pmol/min/g in normal gland to an undetectable level in adenocarcinoma mammae. Of the two main HA degrading enzymes, namely, diamine oxidase and histamine N-methyl-transferase (HMT), only HMT could be detected in mammary gland, either healthy or neoplastic, and its activity was about 5-fold lower in tumor than in the control tissue (1 nmol/g/min vs. 5.2 nmol/g/min). The pattern of changes in histaminergic parameters evoked by the tumor was similar irrespective of the morphological type it represented, characteristics of its vascular bed or whether or not it showed secretory activity.

Histamine in C3H/W mice carrying spontaneous tumors of the mammary gland

Adenocarcinoma mammae, a spontaneously growing mammary cancer in C3H/W mice, contrary to many transplanted tumors does not evoke any rise in histamine level either in the tumor or in distant tissues. On the other hand, the histamine level is reduced by 90% in the tumor in comparison with the healthy gland. This seems to be a consequence of the fall of histidine decarboxylase activity to below a detectable level. There is also a significant reduction in histamine N-methyltransferase activity to one-fifth of the control level. The healthy mammary gland contains a high concentration of histamine and catabolizes it exclusively through the methylation pathway.

Liver damage, voluntary alcohol intake and brain histamine

Liver dysfunction induced by protocaval anastomosis (PCA) in the rat is associated with a great reduction of hepatic alcohol and aldehyde dehydrogenase activities. Despite this, PCA rats voluntarily drank more alcohol than unoperated rats. When subjected to forced alcohol consumption, shunted rats maintained their exaggerated voluntary alcohol intake whereas unoperated rats developed aversion to alcohol. Hypothalamic levels of both histamine and histidine were very high in PCA rats. When these rats were chronically exposed to alcohol, there was a slight decrease in hypothalamic histidine concentration and consequently a lower histamine content. Chronic exposure to alcohol did not, however, influence hypothalamic tissue levels of histamine or histidine in unoperated rats. In both groups, chronic alcohol treatment exerted a stimulatory effect on hepatic alcohol metabolizing enzymes.

Brain histamine in rats with hepatic encephalopathy

Chronic liver failure induced by portocaval anastomosis (PCA) in Wistar rats resulted in a dramatic increase in histamine concentration in hypothalamus and a smaller, but clearly pronounced, elevation in the rest of brain. Between 10 and 120 days following surgery, shunted rats exhibited a histamine level 2.4- to 13-fold higher in hypothalamus and 1.5- to 2.5-fold higher in the rest of brain as compared to their control, sham-operated pairs. There were no significant changes in histamine concentration in the other examined tissues. The increase in brain histamine could not be attributed to the inhibition of its degradation, because activity of histamine N-methyltransferase remained unchanged for at least 40 days. Although the activity of histidine decarboxylase also remained unchanged when measured at a saturating concentration of L-histidine, the increase in histamine content in brain seems to be due to its enhanced synthesis brought about by increased availability of L-histidine in the tissue, as indicated by two to four times higher concentrations of this amino acid in PCA rats.

Histamine metabolism in diabetic rats

Streptozotocin-induced diabetes in rats has been used to study the effect of insulin deficiency on histamine metabolism. There were significant increases in the amine content in the pancreas and intestine, and a significant drop in intestinal diamine oxidase (DAO) activity. The reduced DAO activity may be of clinical relevance.

Histamine catabolism in proliferating skin

The histamine (HI) content and the activities of the enzymes involved in its degradation have been studied in guinea pig skin after stimulation of epidermal proliferation. As compared with unstimulated skin the HI content and histamine N-methyltransferase (HMT) activity in the stripped skin were reduced at the time of increased epidermal proliferation and were higher than the normal when the epidermis becomes hyperplastic. Diamine oxidase (DAO) followed an inverse pattern.

Polyamine levels in sarcoma-bearing rats in relation to growth and necrosis of the tumour cells

Putrescine (PU), spermidine (SPD) and spermine (SPM) levels in blood serum of MC Sa 1828 P-bearing rats have been studied in relation to tumour weight and the histological picture. A statistically significant increase of PU and SPD was found in the course of tumour development. Decrease in the level of polyamines in the necrosis stage was also found. Only increased SPD level appeared in the period of intensified necrosis, accompanied by lymphocyte infiltration.

3H-mepyramine binding and histamine-stimulated cAMP accumulation in mammalian retina

The specific binding of different amounts of 3H-mepyramine to the bovine retina revealed a quasi-hyperbolic curve which approached saturation at 3H-ligand concentration over 9-12 nM. Scatchard analysis of the binding data showed two binding sites with KD values of 0.76 nM and 7.3 nM and Bmax of 49.3 and 194.6 fmole/mg protein, respectively. In the guinea-pig brain 3H-mepyramine bound to a single population of binding sites with KD value of 1.6 nM and Bmax of 291 fmole/mg protein. Various H1-antihistamines were potent competitors of the 3H-mepyramine binding: there was a big difference in potency of d- and 1-chlorpheniramine in both membrane preparations. In the rabbit retina slices histamine, in contrast to dopamine, weakly stimulated cAMP accumulation. The data suggest that the mammalian retina may possess histamine receptors.

Distribution and localization of histamine in bovine and rabbit eye

Histamine (HI) is present in various structures of the bovine and rabbit eye (retina, choroid, sclera) and in the optic nerve of both species. The amine levels in particular structures of either cow or rabbit are highly differentiated, as well as profile of HI distribution which differs markedly between both species, except only the retina structure (HI levels were between 70-80 ng per g tissue). In the bovine retina HI is stored in non mast cell compartment, while in the optic nerve at least 50% of the amine is of mast cell origin. Approximately 90% of the retinal HI was recovered in the P1 subcellular fraction. HI in the bovine retina is metabolized by methylation. The data are discussed in terms of a possible physiological role of HI in the retina.

The histamine-induced skin reaction in schizophrenic and normal subjects

Most published data on histamine skin tests on schizophrenic patients show them to be insensitive relative to normals or other psychotic patients. However, experimental conditions have varied and in most cases only a single dose of histamine was used. We have compared 13 volunteer controls and 16 paranoid schizophrenics; each subject was injected intradermally with histamine, 10, 20, and 50 microgram, doses predetermined in volunteers to give a dose-response curve. Wheal and flare were measured at 10 and 20 minutes, intervals near the time of maximum flare. We found no statistically significant differences between normal controls and schizophrenic patients.

Involvement of diamine oxidase in catabolism of 14C-putrescine in mice in vivo with special reference to the formation of gamma-aminobutyric acid

Tissues of mice killed 2.5 or 30 min after injection of 14C-putrescine, contained 14C-gamma-aminobutyric acid, an unidentified 14C-compound, and unchanged 14C-putrescine. In mice pretreated with aminoguanidine, a powerful inhibitor of diamine oxidase, and then with 14C-putrescine, tissue levels of the radioactive catabolites, gamma-aminobutyric acid and the unidentified compound were markedly reduced. The data suggest that diamine oxidase is involved in the first step of putrescine metabolism and that intestine is the main site for this step. This and other aspects of putrescine metabolism are discussed.

Effects of the histamine H2-receptor agonists dimaprit and 4-methylhistamine on the central noradrenaline and serotonin system

Effects of dimaprit and 4-methylhistamine, two histamine H2-receptor agonists, on noradrenaline and serotonin systems in the rat brain were investigated. Administration of dimaprit into the lateral brain ventricle produced 30% decrease in hypothalamal noradrenaline. 2 h after administration of dimaprit the level of 3-methoxy-4-hydroxyphenylglycol was increased by 50%. 4-Methylhistamine and histamine produced qualitatively the same effects as dimaprit. Dimaprit and 4-methylhistamine increased locomotor activity in tranylcypromine-treated rats. The hyperkinetic action of both drugs was prevented by phenoxybenzamine. Dimaprit had negligible effect on the serotonin system while 4-methylhistamine and histamine decreased serotonin and simultaneously increased 5-hydroxyindolcacetic acid. 4-Methylhistamine and histamine, but not dimaprit, evoked head-twitches in tranylcypromine-treated rats. It is concluded that dimaprit and 4-methylhistamine act similarly on the noradrenaline system, probably releasing noradrenaline, but having different effects on the serotonin system. 4-Methylhistamine (and histamine) probably releases serotonin from rat hypothalamus while dimaprit does not. The results are discussed in relation to a possible interaction of histamine with both noradrenaline and serotonin systems in the rat brain.