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Biomedical subjects

M G Currie

Publications and source records attributed to M G Currie.

At least 19 recordsLinked to original sources
PubMed2000

Uroguanylin treatment suppresses polyp formation in the Apc(Min/+) mouse and induces apoptosis in human colon adenocarcinoma cells via cyclic GMP.

The enteric peptides, guanylin and uroguanylin, are local regulators of intestinal secretion by activation of receptor-guanylate cyclase (R-GC) signaling molecules that produce cyclic GMP (cGMP) and stimulate the cystic fibrosis transmembrane conductance regulator-dependent secretion of Cl- and HCO3-. Our experiments demonstrate that mRNA transcripts for guanylin and uroguanylin are markedly reduced in colon polyps and adenocarcinomas. In contrast, a specific uroguanylin-R-GC, R-GCC, is expressed in polyps and adenocarcinomas at levels comparable with normal colon mucosa. Activation of R-GCC by uroguanylin in vitro inhibits the proliferation of T84 colon cells and elicits profound apoptosis in human colon cancer cells, T84. Therefore, down-regulation of gene expression and loss of the peptides may interfere with renewal and/or removal of the epithelial cells resulting in the formation of polyps, which can progress to malignant cancers of the colon and rectum. Oral replacement therapy with human uroguanylin was used to evaluate its effects on the formation of intestinal polyps in the Min/+ mouse model for colorectal cancer. Uroguanylin significantly reduces the number of polyps found in the intestine of Min/+ mice by approximately 50% of control. Our findings suggest that uroguanylin and guanylin regulate the turnover of epithelial cells within the intestinal mucosa via activation of a cGMP signaling mechanism that elicits apoptosis of target enterocytes. The intestinal R-GC signaling molecules for guanylin regulatory peptides are promising targets for prevention and/or therapeutic treatment of intestinal polyps and cancers by oral administration of human uroguanylin.

Adenocarcinoma↗
PubMed2000

Selective inhibition of inducible nitric oxide synthase reduces progression of experimental osteoarthritis in vivo: possible link with the reduction in chondrocyte apoptosis and caspase 3 level.

OBJECTIVE: To evaluate the in vivo therapeutic efficacy of N-iminoethyl-L-lysine (L-NIL), a selective inhibitor of inducible nitric oxide synthase, on the progression of structural lesions in the experimental canine model of osteoarthritis (OA), and to explore the effect of L-NIL on the level of chondrocyte apoptosis and of important proteins involved in the apoptotic phenomenon, i.e., caspase 3 (inducer) and Bcl-2 (inhibitor). METHODS: The OA model was created by sectioning the anterior cruciate ligament. Dogs were placed into 4 experimental groups: unoperated dogs that received no treatment (controls), operated (OA) dogs that received placebo treatment, OA dogs that received oral L-NIL at 10 mg/kg/day, and OA dogs that received oral L-NIL at 1.0 mg/kg/day. In both L-NIL groups, treatment started immediately after surgery. The OA dogs were killed at 12 weeks after surgery. RESULTS: OA dogs treated with L-NIL showed a reduction in the size of osteophytes and a significant decrease in the severity of macroscopic and histologic cartilage lesions on both condyles and plateaus, compared with untreated OA dogs. L-NIL treatment also significantly decreased metalloprotease activity in cartilage. Immunohistochemical analysis revealed that the levels of chondrocyte apoptosis, caspase 3, and Bcl-2 were markedly increased in OA cartilage (P < 0.0001). A positive correlation between the levels of chondrocyte apoptosis and levels of caspase 3 was found (r = 0.54, P < 0.0001). OA dogs treated with the higher dosage L-NIL showed significantly reduced levels of chondrocyte apoptosis (P < 0.003) and caspase 3 (P < 0.04), but no effect on the increased level of Bcl-2 was demonstrated. CONCLUSION: This study shows that L-NIL reduces the progression of experimental OA. This effect could be related to a reduced level of chondrocyte apoptosis and is likely mediated by a decrease in the level of caspase 3 activity. A sparing effect of L-NIL on the increased level of Bcl-2 may also be a contributing factor.

Animals↗
PubMed1999

A nonpeptidyl mimic of superoxide dismutase with therapeutic activity in rats.

Many human diseases are associated with the overproduction of oxygen free radicals that inflict cell damage. A manganese(II) complex with a bis(cyclohexylpyridine)-substituted macrocyclic ligand (M40403) was designed to be a functional mimic of the superoxide dismutase (SOD) enzymes that normally remove these radicals. M40403 had high catalytic SOD activity and was chemically and biologically stable in vivo. Injection of M40403 into rat models of inflammation and ischemia-reperfusion injury protected the animals against tissue damage. Such mimics may result in better clinical therapies for diseases mediated by superoxide radicals.

Animals↗
PubMed1999

Protective effects of a superoxide dismutase mimetic and peroxynitrite decomposition catalysts in endotoxin-induced intestinal damage.

1. The relative contributions of superoxide anion (O2-) and peroxynitrite (PN) were evaluated in the pathogenesis of intestinal microvascular damage caused by the intravenous injection of E. coli lipopolysaccharide (LPS) in rats. The superoxide dismutase mimetic (SODm) SC-55858 and the active peroxynitrite decomposition catalysts 5,10,15,20-tetrakis(2,4,6-trimethyl-3,5-disulphonatophenyl)-por phyrinato iron (III) and 5,10,15,20-tetrakis(N-methyl-4'-pyridyl)-porphyrinato iron (III) (FeTMPS, FeTMPyP respectively) were used to assess the roles of O2- and PN respectively. 2. The intravenous injection of LPS elicited an inflammatory response that was characterized by a time-dependent infiltration of neutrophils, lipid peroxidation, microvascular leakage (indicative of microvascular damage), and epithelial cell injury in both the duodenum and jejunum. 3. Administration of the SODm SC-55858, FeTMPS or FeTMPyP at 3 h post LPS reduced the subsequent increase in microvascular leakage, lipid peroxidation and epithelial cell injury. Inactive peroxynitrite decomposition catalysts exhibited no protective effects. Only, SC-55858 inhibited neutrophil infiltration. 4. Our results suggest that O2 and peroxynitrite play a significant role in the pathogenesis of duodenal and intestinal injury during endotoxaemia and that their remoyal by SODm and peroxynitrite decomposition catalysts offers a novel approach to the treatment of septic shock or clinical conditions of gastrointestinal inflammation. Furthermore, the remarkable protection of the intestinal epithelium by these agents suggests their use during chemo- and radiation therapy, cancer treatments characterized by gastrointestinal damage. Potential mechanisms through which these radicals evoke damage are discussed.

Animals↗
PubMed1999

Reduction in the structural changes of experimental osteoarthritis by a nitric oxide inhibitor.

OBJECTIVE: To evaluate the in-vivo therapeutic efficacy of N -iminoethyl-L-Lysine (L-NIL), a selective inhibitor of inducible nitric oxide synthase (iNOS) in a dose response study, on the progression of lesions in the experimental osteoarthritic (OA) dog model. DESIGN: The sectioning of the anterior cruciate ligament of the right stifle joint of mongrel dogs was done by a stab wound. Dogs were separated into experimental groups: Group 1 received no treatment, Groups 2, 3, and 4 received oral L-NIL (0.3, 1 or 10mg/kg/day, respectively) starting immediately after surgery. The OA dogs were killed at 12 weeks after surgery. RESULTS: Macroscopically, L-NIL decreased the size of the cartilage lesions on condyles and plateaus. The histologic severity of the cartilage lesions was decreased in the L-NIL-treated dogs. This effect was more pronounced at the highest dosage tested (3 and 10mg/kg/day). CONCLUSIONS: This study confirms the effectiveness of L-NIL, a selective inhibitor of iNOS, in attenuating the progression of experimental OA. It also clearly shows that the effect is dose-dependent.

Animals↗
PubMed1999

Selective inhibition of inducible nitric oxide synthase in experimental osteoarthritis is associated with reduction in tissue levels of catabolic factors.

OBJECTIVE: We used the experimental dog model of osteoarthritis (OA) to examine the in vivo effects of N-iminoethyl-L-lysine (L-NIL), a selective inhibitor of the inducible nitric oxide synthase (iNOS), on the tissue level and distribution of interleukin-1beta (IL-1beta), collagenase-1, stromelysin-1, cyclooxygenase-2 (COX-2), iNOS and nitrotyrosine, through immunohistochemical and morphometric analysis. METHODS: Cartilage and synovial membrane specimens were obtained from 3 experimental groups of dogs: Group I--unoperated dogs that received no treatment; Group II--dogs subjected to a sectioning of the anterior cruciate ligament of the right knee and given no treatment; and Group III--operated dogs that received oral treatment with L-NIL (10 mg/kg twice daily/po) for 10 weeks starting immediately after surgery. The operated dogs were killed 10 weeks post-surgery. The tissue distributions of IL-1beta, metalloproteases (MMP), COX-2, iNOS and nitrotyrosine were documented by immunohistochemistry using specific antibodies, and quantified by morphometric analysis. RESULTS: In cartilage, the cell scores (percentage of chondrocytes staining positive for the antigen) for iNOS and 3-nitrotyrosine were dramatically enhanced in OA specimens compared to normal (p < 0.0001). However, the cartilage of dogs treated with L-NIL showed significantly lower cell scores for iNOS (p<0.0001, condyle; p<0.001, plateau), nitrotyrosine (p<0.0004; p<0.0001) and COX-2 (p<0.0001; p<0.001) compared to that of untreated OA dogs. Similar findings were observed for collagenase-1 and stromelysin-1, where the increased cell scores of these 2 MMP in OA cartilage were reduced after treatment with L-NIL (collagenase: p<0.002, condyle; p<0.0003, plateau; stromelysin: p<0.006; p<0.0001). The increased cell scores for the IL-1beta, COX-2, iNOS and nitrotyrosine found in the synovial lining and mononuclear cell infiltrate of operated animals were also found to be markedly reduced in dogs treated with L-NIL. CONCLUSION: Our study demonstrates for the first time in vivo in an experimental model of OA, that a selective inhibition of iNOS by L-NIL and the subsequent decreased production of NO also results in a marked decrease in production of major catabolic factors such as MMP, IL-1beta and peroxynitrite, as well as a reduction in COX-2 expression.

Animals↗
PubMed1998

2-Iminopyrrolidines as potent and selective inhibitors of human inducible nitric oxide synthase.

A series of substituted 2-iminopyrrolidines has been prepared and shown to be potent and selective inhibitors of the human inducible nitric oxide synthase (hiNOS) isoform versus the human endothelial nitric oxide synthase (heNOS) and the human neuronal nitric oxide synthase (hnNOS). Simple substitutions at the 3-, 4-, or 5-position afforded more potent analogues than the parent 2-iminopyrrolidine 1. The effect of ring substitutions on both potency and selectivity for the different NOS isoforms is described. Substitution at the 4- and 5-positions of the 2-iminopyrrolidine yielded both potent and selective inhibitors of hiNOS. In particular, (+)-cis-4-methyl-5-pentylpyrrolidin-2-imine, monohydrochloride (20), displayed potent inhibition of hiNOS (IC50 = 0.25 microM) and selectivities of 897 (heNOS IC50/hiNOS IC50) and 13 (hnNOS IC50/hiNOS IC50). Example 20 was shown to be an efficacious inhibitor of NO production in the mouse endotoxin assay. Furthermore, 20 displayed in vivo selectivity, versus heNOS isoform, by not elevating blood pressure at multiples of the effective dose in the mouse.

Animals↗
PubMed1998

Characterization of the cytoprotective action of peroxynitrite decomposition catalysts.

The formation of the powerful oxidant peroxynitrite (PN) from the reaction of superoxide anion with nitric oxide has been shown to be a kinetically favored reaction contributing to cellular injury and death at sites of tissue inflammation. The PN molecule is highly reactive causing lipid peroxidation as well as nitration of both free and protein-bound tyrosine. We present evidence for the pharmacological manipulation of PN with decomposition catalysts capable of converting it to nitrate. In target cells challenged with exogenously added synthetic PN, a series of metalloporphyrin catalysts (5,10,15,20-tetrakis(2,4,6-trimethyl-3, 3-disulfonatophenyl)porphyrinato iron (III) (FeTMPS); 5,10,15, 20-tetrakis(4-sulfonatophenyl)porphyrinato iron (III) (FeTPPS); 5,10, 15,20-tetrakis(N-methyl-4'-pyridyl)porphyrinato iron (III) (FeTMPyP)) provided protection against PN-mediated injury with EC50 values for each compound 30-50-fold below the final concentration of PN added. Cytoprotection was correlated with a reduction in the level of measurable nitrotyrosine. In addition, we found our catalysts to be cytoprotective against endogenously generated PN in endotoxin-stimulated RAW 264.7 cells as well as in dissociated cultures of hippocampal neurons and glia that had been exposed to cytokines. Our studies thus provide compelling evidence for the involvement of peroxynitrite in cytokine-mediated cellular injury and suggest the therapeutic potential of PN decomposition catalysts in reducing cellular damage at sites of inflammation.

Animals↗
PubMed1998

2-Iminohomopiperidinium salts as selective inhibitors of inducible nitric oxide synthase (iNOS).

An attractive approach to the treatment of inflammatory conditions such as osteo- and rheumatoid arthritis, inflammatory bowel disease, and sepsis is through the selective inhibition of human inducible nitric oxide synthase (hiNOS) since localized excess nitric oxide (NO) release has been implicated in the pathology of these diseases. A series of monosubstituted iminohomopiperidinium salts possessing lipophilic functionality at ring positions 3, 5, 6, and 7 has been synthesized, and series members have demonstrated the ability to inhibit the hiNOS isoform with an IC50 as low as 160 nM (7). Compounds were found that selectively inhibit hiNOS over the human endothelial constitutive enzyme (heNOS) with a heNOS/hiNOS IC50 ratio in excess of 100 and as high as 314 (9). Potencies for inhibition of hiNOS and the human neuronal constitutive enzyme (hnNOS) are comparable. Substitution in the 3 and 7 positions provides compounds that exhibit the greatest degree of selectivity for hiNOS and hnNOS over heNOS. Submicromolar potencies for 6 and 7 in a mouse RAW cell assay demonstrated the ability of these compounds to inhibit iNOS in a cellular environment. These latter compounds were also found to be orally bioavailable and efficacious due to their ability to inhibit the increase in plasma nitrite/nitrate levels in a rat LPS model.

Administration, Oral↗
PubMed1998

Peroxynitrite decomposition catalysts: therapeutics for peroxynitrite-mediated pathology.

Inflamed tissue is often characterized by the production of NO and superoxide. These radicals react at diffusion-limited rates to form the powerful oxidant peroxynitrite (PN). When protonated, PN decomposes into either nitrate or reactive intermediates capable of mediating tissue damage by oxidation of protein, lipid, and nucleic acid. We recently have identified porphyrin derivatives capable of catalyzing an increase in nitrate formation with a concomitant decrease in the HO.-like and NO2.-like reactivity of PN. Here, we present evidence for the efficacy of these PN decomposition catalysts both in vitro and in vivo. Cells in culture were protected from exogenously added PN by the catalyst 5,10,15,20-tetrakis(2,4, 6-trimethyl-3,5-disulfonatophenyl)porphyrinato iron (III), whereas free iron and the structurally related compound without iron 5,10,15, 20-tetrakis(2,4,6-trimethyl-3,5-disulfonatophenyl)porphyrin did not protect. Cytoprotection correlated well with a reduction in the nitrotyrosine content of released cytosolic proteins, a biochemical marker for PN formation. Carrageenan-induced paw edema is a model of acute inflammation in which PN may play a major role. When tested in this system, both 5,10,15,20-tetrakis(2,4,6-trimethyl-3, 5-disulfonatophenyl)porphyrinato iron (III) and 5,10,15, 20-tetrakis(N-methyl-4'-pyridyl)porphyrinato iron (III) caused a dose-dependent reduction in swelling and lactate dehydrogenase release as well as a detectable shift to nitrate formation in paw tissue. In addition, the catalysts did not elevate mean arterial pressure, suggesting a lack of interaction with NO. Taken together, our data provide compelling evidence supporting the therapeutic value of manipulating PN pharmacologically. Thus, PN decomposition catalysts may represent a unique class of anti-inflammatory agents.

Animals↗
PubMed1998

Substituted 2-iminopiperidines as inhibitors of human nitric oxide synthase isoforms.

A series of analogues of 2-iminopiperidine have been prepared and shown to be potent inhibitors of the human nitric oxide synthase (NOS) isoforms. Methyl substitutions on the 4-position (3) or 4- and 6-positions (8) afforded the most potent analogues. These compounds exhibited IC50 values of 0.1 and 0.08 microM, respectively, for hiNOS inhibition. Substitution with cyclohexylmethyl at the 6-position (13) afforded an inhibitor that showed the best selectivity for hiNOS versus heNOS (heNOS IC50/hiNOS IC50 = 64). Following oral administration, inhibitors were found to decrease serum nitrite/nitrate levels in an in vivo rat endotoxin assay. This series of 2-iminopiperidines were prepared via the described synthetic methodologies. The effect of ring substitutions on potency and selectivity for this class of cyclic amidines as NOS inhibitors is described.

Animals↗
PubMed1998

Reduced progression of experimental osteoarthritis in vivo by selective inhibition of inducible nitric oxide synthase.

OBJECTIVE: To evaluate the in vivo therapeutic efficacy of N-iminoethyl-L-lysine (L-NIL), a selective inhibitor of inducible nitric oxide synthase (iNOS), on the progression of lesions in an experimental osteoarthritis (OA) dog model. The effect of L-NIL on metalloprotease activity, levels of interleukin-1beta (IL-1beta), prostaglandin E2 (PGE2), and nitrite/nitrate in synovial fluid was determined. METHODS: The OA model was created by sectioning the anterior cruciate ligament of the right stifle joint of mongrel dogs by a stab wound. Dogs were separated into experimental groups: Group 1 was made up of unoperated dogs that received no treatment, group 2 were operated dogs with no treatment, and group 3 were operated dogs that received oral L-NIL (10 mg/kg/twice daily) starting immediately after surgery. The OA dogs were killed at 10 weeks after surgery. RESULTS: Experiments showed that dog OA cartilage explants in culture produced an increased amount of NO (nitrite). Immunohistochemical study demonstrated that this was due to an increased level of iNOS in chondrocytes. OA dogs treated with L-NIL showed a reduction in the incidence of osteophytes compared with the untreated OA dogs (58% versus 92%) as well as in their size (mean +/- SEM 1.92 +/- 0.58 mm versus 5.08 +/- 0.66 mm). Macroscopically, L-NIL decreased the size of the cartilage lesions by approximately 50% both on condyles and plateaus. The histologic severity of both the cartilage lesions and synovial inflammation was significantly decreased in the L-NIL-treated dogs. Treatment with L-NIL also significantly decreased both collagenase and general metalloprotease activity in the cartilage and the levels of IL-1beta, PGE2, and nitrite/nitrate in synovial fluid. CONCLUSION: This study demonstrated the effectiveness of a selective inhibitor of iNOS, L-NIL, in attenuating the progression of experimental OA. The data suggest that L-NIL may act by reducing the activity of metalloproteases in cartilage and the production of IL-1beta by synovium, both of which are known to play a major role in the pathophysiology of OA structural changes.

Animals↗
PubMed1998

Natriuretic and kaliuretic activities of guanylin and uroguanylin in the isolated perfused rat kidney.

Guanylin and uroguanylin are novel peptides that activate membrane guanylate cyclases found in the kidney and intestine. We compared the effects of these peptides in the isolated perfused rat kidney. Both peptides are natriuretic and kaliuretic in this preparation. Uroguanylin (0.19-1.9 microM) increased glomerular filtration rate from 0.77 +/- 0.07 to 1.34 +/- 0.3 ml . g-1 . min-1 at the highest concentration. A maximal increase in Na+ excretion was achieved at 0. 66 microM uroguanylin, with a reduction in fractional Na+ reabsorption from 78.7 +/- 1.7 to 58.8 +/- 4.4%. The highest dose of uroguanylin increased kaliuresis by 50%. Osmolar clearance doubled at the highest concentration of uroguanylin tested (P < 0.05). Guanylin also elicited a natriuresis and kaliuresis but appeared to be less potent than uroguanylin. The highest concentration of guanylin (1.3 microM) decreased fractional Na+ reabsorption from 73. 9 +/- 2.4 to 64.5 +/- 4.0%, but lower doses were ineffective. Guanylin stimulated urine K+ excretion at the lowest concentration tested (0.33 microM) without any effect on Na+ excretion. These peptides may influence salt and water homeostasis by biological effects in the kidney that are mediated by the intracellular second messenger, cGMP.

Amino Acid Sequence↗
PubMed1997

Induction of epithelial chloride secretion by channel-forming cryptdins 2 and 3.

Salt and water secretion from intestinal epithelia requires enhancement of anion permeability across the apical membrane of Cl- secreting cells lining the crypt, the secretory gland of the intestine. Paneth cells located at the base of the small intestinal crypt release enteric defensins (cryptdins) apically into the lumen. Because cryptdins are homologs of molecules known to form anion conductive pores in phospholipid bilayers, we tested whether these endogenous antimicrobial peptides could act as soluble inducers of channel-like activity when applied to apical membranes of intestinal Cl- secreting epithelial cells in culture. Of the six peptides tested, cryptdins 2 and 3 stimulated Cl- secretion from polarized monolayers of human intestinal T84 cells. The response was reversible and dose dependent. In contrast, cryptdins 1, 4, 5, and 6 lacked this activity, demonstrating that Paneth cell defensins with very similar primary structures may exhibit a high degree of specificity in their capacity to elicit Cl- secretion. The secretory response was not inhibited by pretreatment with 8-phenyltheophyline (1 microM), or dependent on a concomitant rise in intracellular cAMP or cGMP, indicating that the apically located adenosine and guanylin receptors were not involved. On the other hand, cryptdin 3 elicited a secretory response that correlated with the establishment of an apically located anion conductive channel permeable to carboxyfluorescein. Thus cryptdins 2 and 3 can selectively permeabilize the apical cell membrane of epithelial cells in culture to elicit a physiologic Cl- secretory response. These data define the capability of cryptdins 2 and 3 to function as novel intestinal secretagogues, and suggest a previously undescribed mechanism of paracrine signaling that in vivo may involve the reversible formation of ion conductive channels by peptides released into the crypt microenvironment.

Amino Acid Sequence↗
PubMed1997

Regulation of intestinal uroguanylin/guanylin receptor-mediated responses by mucosal acidity.

Guanylin and uroguanylin are intestinal peptides that stimulate chloride secretion by activating a common set of receptor-guanylate cyclase signaling molecules located on the mucosal surface of enterocytes. High mucosal acidity, similar to the pH occurring within the fluid microclimate domain at the mucosal surface of the intestine, markedly enhances the cGMP accumulation responses of T84 human intestinal cells to uroguanylin. In contrast, a mucosal acidity of pH 5.0 renders guanylin essentially inactive. T84 cells were used as a model epithelium to further explore the concept that mucosal acidity imposes agonist selectivity for activation of the intestinal receptors for uroguanylin and guanylin, thus providing a rationale for the evolution of these related peptides. At an acidic mucosal pH of 5.0, uroguanylin is 100-fold more potent than guanylin, but at an alkaline pH of 8.0 guanylin is more potent than uroguanylin in stimulating intracellular cGMP accumulation and transepithelial chloride secretion. The relative affinities of uroguanylin and guanylin for binding to receptors on the mucosal surface of T84 cells is influenced dramatically by mucosal acidity, which explains the strong pH dependency of the cGMP and chloride secretion responses to these peptides. The guanylin-binding affinities for peptide-receptor interaction were reduced by 100-fold at pH 5 versus pH 8, whereas the affinities of uroguanylin for these receptors were increased 10-fold by acidic pH conditions. Deletion of the N-terminal acidic amino acids in uroguanylin demonstrated that these residues are responsible for the increase in binding affinities that are observed for uroguanylin at acidic pH. We conclude that guanylin and uroguanylin evolved distinctly different structures, which enables both peptides to regulate, in a pH-dependent fashion, the activity of receptors that control intestinal salt and water transport via cGMP.

Amino Acid Sequence↗
PubMed1997

Guanylyl cyclase receptors and guanylin-like peptides in reptilian intestine.

Receptors for guanylin and uroguanylin were identified on the mucosal surface of enterocytes lining the intestine of the bobtail skink (Tiliqua rugosa), king's skink (Egernia kingii), and knight anole (Anolis equestris) by receptor autoradiography using 125I-ST (Escherichia coli heat-stable enterotoxin) as the radioligand. Specific, high-affinity binding of 125I-ST to receptors was found on the microvillus border of enterocytes and little or no specific binding of 125I-ST was observed in other strata comprising the gut wall. The American alligator (Alligator mississippensis) also exhibited receptor binding, but unlike the other three species had relatively high levels of apparent nonspecific binding. A comparison of intestinal cGMP accumulation responses between the American alligator and the knight anole demonstrated a greater magnitude of cGMP responses to ST and guanylin in vitro in the knight anole relative to the tissue cGMP accumulation responses of alligators. Treatment with ST resulted in markedly greater tissue cGMP accumulation responses in both species compared to treatment with guanylin. To complete a paracrine signaling pathway in reptilian intestine, guanylin-like peptides that stimulated cGMP accumulation in human T84 intestinal cells were isolated from the intestinal mucosa of alligators. We conclude that functional receptor-guanylyl cyclases and one or more endogenous guanylin/uroguanylin-like peptides occur in the intestinal tract of reptiles as well as in the intestines of mammals and birds. Thus, higher vertebrates have a conserved signaling pathway that regulates intestinal function through the first-messenger peptides, guanylin and/or uroguanylin, and the intracellular second messenger, cGMP.

Amino Acid Sequence↗