Dopa decarboxylase (DDC; aromatic-Lamino-acid decarboxylase; aromatic-L-amino-acid carboxylyase, EC 4.1.1.28) was purified from rat liver and its partial sequence was determined. Synthetic oligonucleotides were used to construct and screen rat liver cDNA libraries, and three clones were isolated and sequenced. The 2 kilobases of DDC cDNA cloned consisted of a 5'-noncoding segment of 78 nucleotides, a coding region of 1440 nucleotides, and a 3'-noncoding region of 438 nucleotides. The encoded protein of 480 amino acid residues had a molecular weight of 54,000. A special feature of the primary structure of rat DDC was a repeating structure consisting of 29 amino acid residues. A sequence of 58 amino acid residues, including this repeating structure of rat DDC, was found to show homologies with those of rat tyrosine hydroxylase, human dopamine j3-hydroxylase, and bovine phenylethanolamine N-methyltransferase, other mammalian enzymes that synthesize catecholamines. These results indicate that catecholamine biosynthetic enzymes are structurally related and suggest that their homologous domains are important for catechol-protein interactions.The biosynthetic pathway of catecholamines has been well established and four enzymes-tyrosine hydroxylase [TH; tyrosine 3-monooxygenase; L-tyrosine, tetrahydropteridine: oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2], dopa decarboxylase (DDC; aromatic-L-amino-acid decarboxylase; aromatic-L-amino-acid carboxy-lyase, EC 4.1.1.28), dopamine P-hydroxylase [DBH; dopamine f3-monooxygenase; 3,4-dihydroxyphenethylamine, ascorbate: oxygen oxidoreductase (P-hydroxylating), EC 1.14.17.1], and phenylethanolamine N-methyltransferase (PNMT; S-adenosyl-L-methionine:phenylethanolamine N-methyltransferase, EC 2.1.1.28)-are known to be involved in biosynthesis of epinephrine from tyrosine. Recently, three of these enzymes (all but DDC) were cloned (1-3) and it became possible to investigate the regulation of these steps of catecholamine synthesis at the molecular level. DDC catalyzes decarboxylation not only of dopa to dopamine but also of 5-hydroxytryptophan to serotonin (4-7), and it is the sole enzyme necessary in both catecholamine and indoleamine biosynthesis. The enzyme is found in neural tissues and also in peripheral organs, especially liver and kidney. But there are no reports concerning the regulation of DDC expression in neural tissue, nor is it known why high activity of DDC is expressed in liver and kidney. Recently, the DDC gene of Drosophila was cloned and sequenced (8), but in Drosophila >90% ofthe DDC is concerned with cuticle sclerotization (9).We have purified rat liver DDC, obtained polyclonal and monoclonal antibodies to it, and determined some of its enzymological properties (10). We have also studied the difference between rat DDC and rat histidine decarboxylase (L-histidine carboxy-lyase, EC 4.1.1.22), which synthesizes histamine (11). Molecular cloning and sequencing of rat DDC cDNA should be useful in understanding the regulation of the mammalian DDC gene,...
Interleukin-1 beta (IL-1 beta) is the most potent inhibitor of gastric acid secretion known at present. Although histamine has been shown to be an important mediator of gastric acid secretion, the effect of IL-1 beta on gastric histamine mobilization has not been studied. In the present study, the effects of IL-1 beta on gastric acid secretion and gastric histamine mobilization were investigated in conscious rats with both gastric and vesical fistulas. IL-1 beta (5 micrograms/kg iv) significantly inhibited basal acid secretion but did not affect basal urinary histamine excretion and fundic histidine decarboxylase (HDC) activity. Gastrin-17-I (1 nmol.kg-1.h-1) caused a marked increase in acid secretion, urinary histamine secretion, and fundic HDC activity. IL-1 beta (5 micrograms/kg iv) completely inhibited gastrin-induced acid secretion and partially inhibited urinary histamine excretion and fundic HDC activity. Pretreatment with indomethacin (10 mg/kg ip) partially reversed the inhibitory effects of IL-1 beta on gastrin-stimulated fundic HDC activity and acid secretion. These findings indicate that IL-1 beta inhibits gastric histamine mobilization through both prostaglandin-dependent and prostaglandin-independent pathways. Furthermore, it is suggested that the inhibitory action of IL-1 beta on gastric acid secretion is mediated by the inhibition of gastric histamine mobilization.
The aim of this experiment was to demonstrate whether histamine and histidine decarboxylase (HDC) contribute to mucosal repair in small intestine subjected to ischemia-reperfusion (1/ R). The superior mesenteric artery was occluded for 15 min followed by reperfusion. In jejunal mucosa, histamine content and HDC activity increased after I/R. Histamine output in mesenteric lymph was also elevated after I/R. These increases in HDC activity, and mucosal and lymph histamine levels were suppressed by pretreatment of a-fluoromethylhistidine (a-
Intranasal application of toluene diisocyanate (TDI) induced nasal allergy-like symptoms of sneezing and watery rhinorrhea and decreased the histamine content of the nasal mucosa in guinea pigs. However, in the animals pretreated with capsaicin (capsaicin desensitization) before sensitization with TDI, nasal allergy-like symptoms were not induced. Capsaicin desensitization also inhibited histamine release in the nasal mucosa induced by TDI. These findings suggest that antidromic impulses of capsaicin-sensitive sensory nerves stimulated by TDI cause histamine release from mast cells in the nasal mucosa, resulting in nasal discharge and sneezing in guinea pigs. Thus neurogenic inflammation via an axon reflex in the nose may contribute to the pathogenesis of vasomotor rhinitis.
This study was designed to determine whether alanyl glutamine-containing total parental nutrition (TPN) can restore the impaired adaptive process of the remaining intestine, observed with administration of conventional TPN, after massive small-bowel resection. Seventy-four male Sprague-Dawley rats weighing 250 g were randomly divided into seven groups. Group I rats (n = 10) were killed after overnight fasting. Group II animals (n = 32) underwent massive small bowel resection (85%) with preservation of the first 15 cm of jejunum. Group III animals (n = 32) were also submitted to massive small-bowel resection with preservation of 15 cm of terminal ileum. Three different TPN solutions were prepared. Solution A was a conventional formulation that did not contain glutamine. Solution B contained 1.88 times the amino acid concentration of solution A. Solution C was prepared by adding alanyl glutamine (2 g/100 mL) to solution A. Solutions B and C were isonitrogenous and isocaloric. Each solution was infused to groups II and III, which were subdivided into groups IIA (n = 10), IIB (n = 11), IIC (n = 11), IIIA (n = 10), IIIB (n = 11), and IIIC (n = 11). After 1 week of TPN (270 kcal/kg per day), the experimental animals were killed and the intestine was taken for examination. Final body weight did not differ significantly among the groups, and there was no difference in nitrogen balance among the animals that received solution B or C.(ABSTRACT TRUNCATED AT 250 WORDS)
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