[Effect of Z-103 on wound healing by dermal incision in guinea pigs]

We investigated the effects of Z-103, ZnSO4, L-carnosine and solcoseryl on wound healing by dermal incision in guinea pigs. The tensile strength, hydroxyproline contents and the value of angiogenesis (carmine contents) at the wounded site of dorsal skin were used as indices of wound healing. Z-103, given daily s.c., increased the tensile strength and hydroxyproline contents on day 4 after operation in a dose-dependent manner; in particular, the effect of 10 mg/kg of Z-103 was nearly equal to that of solcoseryl at 0.5 ml/animal. Moreover, Z-103 10 mg/kg increased the value of angiogenesis on day 3 after the operation. On the other hand, ZnSO4 and L-carnosine, components of Z-103, also similarly increased the tensile strength and hydroxyproline contents. These results suggest that Z-103 possessed an accelerative action on wound healing, and these effects may be due to the activity of its components, ZnSO4 and L-carnosine.

[Studies on the healing promoting action of Z-103 in chronic gastric ulcer models of rats]

We studied the healing promoting action of Z-103 on the chronic gastric ulcer induced by acetic acid (AAU) or Fe-ascorbic acid (FAU) in rats. The area of the gastric ulcers, hydroxyproline (Hyp) and DNA contents in the ulcer region were measured as an index of ulcer healing. The area of gastric ulcers was the largest on day 4 and thereafter gradually decreased, but the ulcers still remained at the 14th day. Hyp contents in the ulcer region decreased until the 7th day in both models, and then this level increased. Significant decrease in DNA contents in the ulcer region was observed on the 7th day only in FAU. In AAU and FAU, administration of Z-103 (3 mg/kg/day x 2, p.o.) resulted in a significant decrease in the area of gastric ulcers on the 14th day and a significant increase in Hyp contents in the ulcer region on the 7th day as compared with the control group. Z-103 increased the DNA contents in the ulcer region on the 4th day in AAU and on the 7th day in FAU. These results suggest that tissue destruction surrounding the ulcer region in AAU and FAU models might occur until the 4th or 7th day after operation, and that the acceleration of ulcer healing by Z-103 on these models may be facilitated by the wound healing action of this drug.

[The gastric mucosal adhesiveness of Z-103 in rats with chronic ulcer]

The gastric mucosal adhesiveness of Z-103 in rats with acetic acid ulcer was studied macroscopically, histologically, and biochemically. From macroscopical observations, when Z-103 was orally administered to an acetic acid ulcer model, there was adhesion of Zn to the normal mucosa as well as the ulcerous site under both the fasting condition and after feeding. It was also proven that the strength and duration of adhesiveness were increased dose-dependently under fasting conditions. In addition, histological localization of Zn was noted from the covering epithelial cell layer to the gastric lamina propria mucosae in the normal tissue and in the most superficial ulcerous layer and the granulous layer of the ulcerous site. Measurement of the gastric tissue Zn content after oral administration of 100 mg/kg of Zn showed that the Zn content was significantly increased for 6 hr at the normal site and for 24 hr at the ulcerous site. On the other hand, although ZnSO4 and ZnSO4+carnosine combination macroscopically produced generally the same level of adhesiveness as Z-103, when the gastric tissue Zn content for Z-103 and ZnSO4 were compared, the Zn content of ZnSO4 was lower than that for Z-103 at both the normal and ulcerous site. In summary, Z-103 shows a long-term adhesive and permeable action on the gastric mucosa in acetic acid ulcer rats, and it has a comparable high affinity at the ulcerous site.

Experimental metastasis of oncogene-transformed NIH 3T3 cells in chick embryo

By means of a highly sensitive and quantitative assay for specific detection of metastasized tumor cells in chick embryonic organs using the polymerase chain reaction (PCR), we have examined the experimental metastatic ability of individual clones of NIH 3T3 cells, transformed with oncogenes: v-Ki-ras, v-Ha-ras, v-src, v-fos, and v-abl. Such a transformed clone had different metastatic abilities in different embryonic organs. Among them, two clones of NIH 3T3 cells transformed with ras-oncogenes (v-Ki-ras or v-Ha-ras) metastasized to liver and lungs of chick embryo, and grew there more rapidly than the other clones. The parental NIH 3T3 cells were detected as slight bands of PCR products after iv injection, indicating some cells were trapped in chick embryonic organs, but did not grow. These findings indicate that the transformed cells are able to invade the organ tissues and grow in embryonic chick organs, but non-metastatic cells such as the untransformed-NIH 3T3 cells are not able to grow in the secondary sites. These experiments clearly demonstrate the usefulness of this assay system to study genes involved in malignant transformation.

Expression of genes encoding type IV collagen-degrading metalloproteinases and tissue inhibitors of metalloproteinases in various human tumor cells

Uncontrolled expression of matrix metalloproteinases 2, 3 and 9 (MMP-2, -3 and -9) is believed to be a critical part of the invasive potential of tumor cells because of their ability to degrade type IV collagen, a major structural component of basement membranes. Availability of proteolytic activity in the vicinity of the cell surface is further affected by a local balance between the enzymes and their inhibitors produced by the cell. To determine how frequently deregulated expression of the MMPs and tissue inhibitors of metalloproteinases (TIMPs) is associated with tumor cells, 26 human tumor cell lines were examined by Northern blotting. Transcripts for MMP-2 and MMP-9 were more frequently expressed in mesenchymal tumor cells (9/9 for MMP-2 and 6/9 for MMP-9) than in epithelial tumor cells (4/17 for MMP-2 and 2/17 for MMP-9). Although expression of MMP-2 mRNA was clearly cell type-specific, MMP-9 mRNA expression in mesenchymal cells correlated well with the reported tumorigenicity of the cells. Enhanced expression of MMP-9 mRNA was also associated with the tumorigenic transformation of cells by an activated c-H-ras gene in human embryonic fibroblasts. Only 3 of the 26 tumor cells expressed MMP-3 mRNA, and 2 of the 3 were epithelial tumor cells which coordinately expressed MMP-9 and TIMP-1 mRNAs. TIMP-1 mRNA was almost undetectable in 50% of the tumor cells, but TIMP-2 mRNA was expressed in the majority of the cells. These findings provide comprehensive information about mRNA expression of the MMPs and TIMPs in tumor cells, the deregulation of which is thought to be an integral part of the invasive potential of tumor cells.

HTLV-1 Tax has distinct but overlapping domains for transcriptional activation and for enhancer specificity

Tax1 of human T-cell leukemia virus type 1 (HTLV-1) activates viral transcription dependent upon three 21-bp enhancer elements in the long terminal repeat. Difficulties in detecting any association of Tax1 with the viral enhancer have hampered elucidation of the molecular mechanisms of Tax1-mediated transcriptional activation. By constructing a fusion protein with the heterologous DNA-binding domain of yeast GAL4, Tax1 was shown to be a potent transcriptional activator dependent on the presence of GAL4-binding sites. Deletions of the Tax1 portion of the fusion protein revealed that almost the entire region of Tax1 (amino acids 2-337) is required for activation, and the activity correlated well with that of the viral enhancer. The GAL/Tax1 mutant lacking 41 residues of the C-terminus of Tax1, GAL/Tax1(2-312), was inactive for the viral enhancer, but activity was recovered by adding the heterologous activation domain of herpes simplex virus VP16. These results indicate that Tax1 has two distinct but overlapping functional domains for transcriptional activation and for enhancer specificity. Thus, Tax1 is thought to be a transcription factor acting in the enhancer complex rather than as a catalytic or allosteric modifier of pre-existing cellular transcription factors.

Comparison of autocrine mechanisms promoting motility in two metastatic cell lines: human melanoma and ras-transfected NIH3T3 cells

Tumor-cell migration plays an essential role in invasion into surrounding tissues and the formation of metastatic colonies in distant organs. Metastatic human A2058 melanoma and ras-transfected NIH3T3 cells produce autocrine motility factors (AMFs) which stimulate their own motility, and the A2058 cell AMF (AMF/A2058) has been purified. In this study, we partially purified the AMF produced by N-ras-transfected NIH3T3 cells (AMF/NIH3T3) and compared it with AMF/A2058. The two AMFs differed in their gel filtration patterns and heat stability, although both elicited migration of N-ras-transfected NIH3T3 cells. The receptor for AMF/A2058 in A2058 cells is linked to a pertussis-toxin-sensitive GTP-binding protein. Pre-treatment of N-ras-transfected NIH3T3 cells with pertussis toxin also specifically blocked the promotion of motility by AMF/A2058, but did not affect the activity of AMF/NIH3T3. Stimulation of N-ras-transfected NIH3T3 cells by both AMFs elicited an additive response. Thus, the autocrine mechanisms of these two metastatic tumor cell lines are different with regard to the AMF molecules, receptors, and signal transduction pathways.

HTLV-1 Tax induces expression of various immediate early serum responsive genes

Human T-cell leukemia virus type 1 (HTLV-1) is an etiological agent of adult T-cell leukemia (ATL). We showed here by mobility-shift assay that T-cell lines transformed with the virus contained high levels of AP-1 activities. Consistent with this result, these cell lines expressed increased levels of mRNAs encoding the AP-1 proteins, c-Fos, Fra-1, c-Jun, JunB, and JunD. Previously, transcription of the c-fos gene has been reported to be transactivated by the viral transcription factor, Tax1. By using the human T-cell line (JPX-9), in which expression of the Tax1 is inducible, we showed that expression of mRNAs for Fra-1, c-Jun, and JunD was also transactivated by Tax1. Moreover, Tax1 activated expression of two other transcription factors having zinc finger motifs, Egr-1 and Egr-2, in the same cells. The Tax1-inducible transcription factors identified here are encoded by the members of immediate early genes under the control of growth signals. Thus, Tax1 was suggested to replace growth signals, at least in part, by this mechanism.

Antiulcer agents. II. Synthesis and gastric acid antisecretory activity of N-[3-(3-(piperidinomethyl)phenoxy)propyl]-4-(1-methyl-1H- tetrazol-5-ylthio)butanamide and related compounds

N-[3-(3-(Piperidinomethyl)phenoxy)propyl]butanamides having a 1-methyl-1H-tetrazol-5-ylthio moiety as a pharmacophore and related compounds were prepared and tested for their antisecretory activity against histamine-induced gastric acid secretion in conscious rats with gastric fistulas. Most of the compounds showed antisecretory activity. Among them, N-[3-(3-(piperidinomethyl)phenoxy)propyl]-4-(1-methyl-1 H-tetrazol-5-ylthio)butanamide (5f) was found to posses the most potent activity, and a possibility of isosteric replacement of the methoxycarbonyl group with 1-methyl-1H-tetrazol-5-yl group was indicated. The structure-activity relationships are also discussed.

A novel fibrinolytic enzyme extracted from the earthworm, Lumbricus rubellus

A strong fibrinolytic enzyme was readily obtained in saline extracts of the earthworm, Lumbricus rubellus. It hydrolyzed not only plasminogen-rich fibrin plates, but also plasminogen-free fibrin plates. The average fibrinolytic activity was about 100 CU (plasmin units) or 250 IU (urokinase units)/g wet weight. The molecular weight and isoelectric point were about 20,000 and 3.4, respectively. The enzyme was heat-stable and displayed a very broad optimal pH range. DFP and SBTI strongly inhibited the enzyme, but the anti-plasmin agent, t-AMCHA, exerted little effect under the same conditions. Purification of the enzyme was performed and three partially purified fractions were obtained. These three fractions were further subdivided. The first fraction (F-I) was divided into three fractions (F-I-0, F-I-1, and F-I-2), which exhibited similar biochemical characteristics. The second fraction (F-II) could not be subdivided. The third fraction (F-III) was divided into two fractions (F-III-1 and F-III-2). Based on results for their enzymatic activities against various substrates, the fraction I enzymes are thought to represent a chymotrypsin-like enzyme and the fraction III enzymes to represent a trypsin-like enzyme. The fraction II enzyme appears to be neither a trypsin- or chymotrypsin-like enzyme nor an elastase. The amino acid compositions of the six enzymes were estimated. Compared with other serine enzymes, these enzymes contained very abundant asparagine or aspartic acid, and there was very little proline or lysine. From the above data, these enzymes are regarded as novel fibrinolytic enzymes, and we name them collectively as Lumbrokinase from the generic name of the earthworm.

Synthesis and pharmacological properties of N-[3-(3-(1-Piperidinylmethyl)phenoxy)propyl]-2-(2-hydroxyethylthio)- acetamide and related compounds as antiulcer agents. I

N-Phenoxypropylacetamide derivatives were prepared and tested for antiulcer activity. These compounds exhibited both gastric acid antisecretory and cytoprotective properties. Structure-activity studies led to the identification of N-[3-(3-(1-piperidinylmethyl)phenoxy)propyl]-2-(2-hydroxyethylt hio)acetamide (8), which was selected for further development and clinical evaluation.

Retrovirus from human T-cell leukemia virus type I-associated myelopathy is the same strain as a prototype human T-cell leukemia virus type I

A retrovirus was isolated from a T-cell line that was established from lymphocytes in the cerebrospinal fluid of a patient with human T-cell leukemia virus type I-associated myelopathy (HAM), and its genome was sequenced. The nucleotide sequence of the 3' half of the total genome was identical in 99.5% of the nucleotides to that of the prototype human T-cell leukemia virus type I that was derived from a patient with adult T-cell leukemia. These results indicate that the same retrovirus human T-cell leukemia virus type I is associated with both a neurological disease, HAM, and a lymphoproliferative disease, adult T-cell leukemia.

Induction and stimulation of 92-kDa gelatinase/type IV collagenase production in osteosarcoma and fibrosarcoma cell lines by tumor necrosis factor alpha

Production of a 92-kDa gelatinase/type IV collagenase and tissue inhibitor of metalloproteinases (TIMP) was investigated with human sarcoma cell lines. Among the cytokines and growth factors examined, only human recombinant tumor necrosis factor alpha (TNF alpha) induced and stimulated the proteinase with concomitant increase in TIMP expression, but matrix metalloproteinase 2 (72-kDa gelatinase/type IV collagenase) expression was unchanged. These data suggest that gene expression of the two metalloproteinases is regulated in a different fashion and TNF alpha may be important to allow cancer cells to be more invasive and metastatic.

Secondary structure of the human T-cell leukemia virus type 1 rex-responsive element is essential for rex regulation of RNA processing and transport of unspliced RNAs

Rex protein of human T-cell leukemia virus type 1 (HTLV-1) induces cytoplasmic expression of unspliced gag/pol mRNA and singly spliced env mRNA and thus is essential for replication of the virus. This regulation requires a cis-acting rex-responsive element (RXE), located in the 3' region of the viral RNA. By external deletion, we have identified RXE composed of 205 nucleotides. The secondary structure of RXE was confirmed by studies on its susceptibility to nuclease digestions to consist of four stem-loops and a long stretch of stem structure. Substitution and deletion mutations revealed that two regions of the stem-loops and their secondary structures are essential for rex regulation. Similar secondary structures were found in the corresponding regions of HTLV-2, bovine leukemia virus and human immunodeficiency virus. Furthermore, a sequence of 11 nucleotides in the RXE was found to be conserved in the secondary structures of HTLV-1, HTLV-2, and bovine leukemia virus. These observations suggest that the secondary structure as well as the conserved sequence may be important in expression of unspliced RNA even with diverged sequences as observed in these viruses.

The U5 sequence is a cis-acting repressive element for genomic RNA expression of human T cell leukemia virus type I

The long terminal repeat (LTR) of HTLV-1 consists of U3-R-U5 and contains elements which regulate the viral gene expression. In addition to these elements, we found that the U5 sequence contained a repressive element in the gene expression. Sequential deletions of the LTR substantially increased CAT expression of a LTR-CAT construct. The repressive effect was also observed at RNA level on unspliced RNA, but not on spliced RNA. These differential effects suggest that the U5 element is a cis-acting RNA element, since splicing within the R segment removed the U5 element. In the context of HTLV-1 gene expression, the U5 element would repress expression of unspliced genomic RNA of HTLV-1, but not subgenomic RNA.

Effects of zinc L-carnosine on gastric mucosal and cell damage caused by ethanol in rats. Correlation with endogenous prostaglandin E2

The effects of zinc L-carnosine on ethanol-induced damage and the correlation of these effects with endogenous prostaglandin E2 were evaluated in rat gastric mucosa in vivo and in vitro. When given either intragastrically or intraperitoneally, zinc L-carnosine (10 or 30 mg/kg) prevented gross visible damage to gastric mucosa caused by ethanol without affecting the mucosal prostaglandin E2 level. This protective effect of zinc L-carnosine was not inhibited by indomethacin. Histological assessment showed that zinc L-carnosine inhibited deep mucosal necrosis, as did 16,16-dimethyl prostaglandin E2. Zinc L-carnosine (10(-6) or 10(-5) M) inhibited the damage caused by ethanol to gastric cells isolated from rat gastric mucosa in vitro; this effect was not inhibited by indomethacin. The results suggested that zinc L-carnosine protects the gastric mucosa and enhances cellular resistance to ethanol without the mediation of endogenous prostaglandins.

[Studies on anti-ulcer effects of a new compound, zinc L-carnosine (Z-103)]

We investigated the anti-ulcer effects of zinc L-carnosine (Z-103) using several acute experimental models of gastric and duodenal lesions in rats. Effects of Z-103 on various gastric functions, e.g., antacid (in vitro), anti-pepsin (in vitro), gastric secretion, mucosal potential difference (PD) and mucus contents were also examined. Z-103 given orally prevented development of gastric lesions induced by water immersion stress, histamine, HCl-aspirin, HCl-ethanol and also duodenal ulcers induced by mepirizole in a dose-dependent manner. In vitro, Z-103 had a greater antacid effect than sodium bicarbonate; and moreover, the potency of its anti-peptic action (IC50 = 8.7 mM) was higher than those of several other drugs (sodium bicarbonate, sucrose sulfate and aceglutamide aluminum). Intragastric treatment of Z-103 (100 mg/kg alone tended to increase PD, and it also significantly inhibited the decrease in PD induced by aspirin. In addition, pretreatment with Z-103 at 10 and 30 mg/kg (p.o.) significantly prevented the decrease in mucus contents in the gastric mucosa and also mucosal lesions by oral administration of ethanol. On the other hand, Z-103 was not so effective on both basal (pylorus-ligation preparation) and histamine-stimulated gastric secretion (Heidenhain pouch preparation). These results suggest that Z-103 is useful for the treatment of gastric and duodenal ulcers in humans.

Effects of ammonia on the gastric mucosal barrier in rats and dogs

We examined the effect of ammonia on the gastric mucosal barrier by measuring the changes in transmucosal fluxes of H+, Na+ and K+. In rats, ammonia at concentrations of 0.1 to 0.5% increased the H+ loss from the lumen and 0.2 to 0.5% concentrations of ammonia increased both Na+ and K+ influxes into the lumen. In dogs, in an exactly similar manner to rats, ammonia at concentrations of 0.1 to 0.5% increased H+ loss, and ammonia at concentration of 0.5% increased both Na+ and K+ influxes into the lumen. These results suggest that ammonia breaks the gastric mucosal barrier.

Thymic atrophy characteristic in transgenic mice that harbor pX genes of human T-cell leukemia virus type I

The human T-cell leukemia viruses (HTLV) are associated with T-cell malignancies in humans. The malignant transformation occurs after a long latency in some carriers, and its mechanism appears to be distinct from that of other classes of retroviruses which induce transformation through viral or cellular oncogenes. A widely postulated explanation is that the products of novel pX genes transactivate endogenous cellular genes which lead to tumor development in T cells. To directly examine the pathological effects of pX genes in vivo, we produced transgenic mice harboring the HTLV type I pX genes under several regulatory units: HTLV type I long terminal repeat, immunoglobulin enhancer-simian virus 40 promoter, and mouse mammary tumor virus long terminal repeat. Atrophy of the thymus was characteristic in these mice no matter which regulatory unit directed the expression of the genes.

[Regulation of HTLV-1 gene expression and its relevance to proliferation of the infected cells]

Proliferation of HTLV-1 after infection is one of the crucial steps that affects development of adult T cell leukemia. In addition, one of the regulatory factors, tax protein, activates not only viral transcription from the LTR but also transcription of genes coding IL-2 and IL-2 receptor and eventually supposed to induce proliferation of infected T cells. However, expression of tax protein is regulated negatively by another viral regulatory factor, rex protein, in a novel fashion. The process of ATL development is discussed in relation to the regulation of viral gene expression.

Molecular mechanisms of regulation of HTLV-1 gene expression and its association with leukemogenesis

Human T-cell leukemia virus type 1 (HTLV-1) has two trans-acting regulator genes, tax and rex, in the pX region. The tax gene is a trans-acting transcriptional activator of the long terminal repeat (LTR) and also of the cellular gene for IL-2R alpha. The latter seems to explain initiation of abnormal growth of HTLV-1 infected cells. The rex gene is a posttranscriptional regulator accumulating gag and env mRNA and also indirectly suppressing the transcription. The regulation requires two cis-acting elements, the LTR sequence at the 3' terminus and 5' splice signal, suggesting a novel mechanism of RNA processing in the nucleus. These two trans-activator genes are essential for efficient replication of HTLV-1 and also explain its poor replication competence and tendency to be latent in vivo.

Effect of Z-103 on compound 48/80-induced gastric lesions in rats

Z-103 (a novel anti-ulcer agent), given p.o. at doses of 30 and 100 mg/kg, significantly prevented gastric lesions induced by compound 48/80 in rats. Z-103 inhibited the histamine release from rat peritoneal mast cells stimulated by compound 48/80 in a dose-dependent manner. Z-103 inhibited the increase in thiobarbituric acid (TBA) reactants induced by a single or repeated administration of compound 48/80 in the gastric mucosa. These observations suggested that the protective effect of Z-103 against compound 48/80-induced gastric lesions may be due to its stabilizing activity toward mast cells and/or an antioxidative effect on the gastric mucosa.

Complete nucleotide sequence of the chromosomal gene for human IL-4 and its expression

We have isolated a chromosomal DNA segment of the human IL-4 gene based on homology with a human IL-4 cDNA sequence and determined its complete nucleotide sequence. The human IL-4 gene, which occurs as a single copy in the haploid genome, is mapped on chromosome 5. It is composed of four exons and three introns and is approximately 10 kilobase pairs in size. 5'-Flanking regions of human and mouse IL-4 genes share about 85% homology extending more than 500 base pairs upstream of a "TATA" like sequence. Several patches of sequences are found in the 5'-flanking region of the human IL-4 gene which are homologous to sequence in the 5'-flanking regions of the IL-2, IL-3, IL-5, and granulocyte-macrophage (GM)-CSF genes. The IL-4 gene is inducible after treatment of human T cell clone by phorbol-12-myristate-13-acetate (TPA) and calcium ionophore A23187. The 2.3-kb 5'-flanking region of the human IL-4 gene transiently transfected into Jurkat human T cell leukemia cells is activated efficiently in response to TPA and A23187 stimulation and, although less efficiently, by human T cell leukemia virus type I-encoded p40x or BPV-encoded E2 protein. Combination of TPA/A23187 and p40x or E2 protein further augmented the level of expression.

Complete nucleotide sequence of the chromosomal gene for human IL-4 and its expression

We have isolated a chromosomal DNA segment of the human IL-4 gene based on homology with a human IL-4 cDNA sequence and determined its complete nucleotide sequence. The human IL-4 gene, which occurs as a single copy in the haploid genome, is mapped on chromosome 5. It is composed of four exons and three introns and is approximately 10 kilobase pairs in size. 5'-Flanking regions of human and mouse IL-4 genes share about 85% homology extending more than 500 base pairs upstream of a "TATA" like sequence. Several patches of sequences are found in the 5'-flanking region of the human IL-4 gene which are homologous to sequence in the 5'-flanking regions of the IL-2, IL-3, IL-5, and granulocyte-macrophage (GM)-CSF genes. The IL-4 gene is inducible after treatment of human T cell clone by phorbol-12-myristate-13-acetate (TPA) and calcium ionophore A23187. The 2.3-kb 5'-flanking region of the human IL-4 gene transiently transfected into Jurkat human T cell leukemia cells is activated efficiently in response to TPA and A23187 stimulation and, although less efficiently, by human T cell leukemia virus type I-encoded p40x or BPV-encoded E2 protein. Combination of TPA/A23187 and p40x or E2 protein further augmented the level of expression.

Effects of 16,16-dimethyl-prostaglandin E2 on ammonia- and ethanol-induced mucosal lesions in the rat

The effect of necrotizing agents, such as ammonia and ethanol, on the gastric mucosa was compared. Intragastric administration of ammonia (0.6-1.0%) and ethanol (60-100%) produced hemorrhagic necrosis of gastric mucosa in a concentration-dependent manner. In the anesthetized rat, the macroscopic lesions induced by ethanol were significantly inhibited by pretreatment with 3 or 10 micrograms/kg of 16,16-dmPGE2, but the lesions induced by ammonia were not inhibited by either 3 or 10 micrograms/kg of 16,16-dmPGE2 in the anesthetized rat. The decrease of gastric transmucosal potential difference and mucosal blood flow produced by ethanol (100%) were significantly attenuated by 16,16-dmPGE2; however, those produced by ammonia (1%) were not inhibited by 16,16-dmPGE2 in the anesthetized rat. In conscious rats, ammonia-induced lesions were not inhibited by pretreatment with 3 micrograms/kg of 16,16-dmPGE2 but they were significantly reduced by the pretreatment of 10 micrograms/kg of 16,16-dmPGE2. These results show that 16,16-dmPGE2 afforded little protection against ammonia-induced gastric lesions in the anesthetized rat and suggest that a different mechanism is involved in the development of gastric mucosal lesions between those induced by ethanol and those induced by ammonia.