Biomedical subjects

S R Lin

Publications and source records attributed to S R Lin.

At least 19 recordsLinked to original sources

PubMed1997

Probing calcium ion-induced conformational changes of Taiwan cobra phospholipase A2 by trinitrophenylation of lysine residues.

Phospholipase A2 (PLA2) from Naja naja atra (Taiwan cobra) snake venom was subjected to lysine modification with trinitrobenzene sulfonate (TNBS). Three major derivatives, TNP-1, TNP-2, and TNP-3, were separated by high-performance liquid chromatography (HPLC) from the reaction mixtures in the absence of Ca2+. However, only TNP-2 and TNP-3 were isolated when trinitrophenylated reaction was carried out in the presence of Ca2+. TNP-1 and TNP-2 contained only one TNP group, on Lys-65 and Lys-6, respectively; and both Lys-6 and Lys-65 were modified in TNP-3. The extent of modification on Lys-6 and Lys-65 was calculated from the peak areas of TNP proteins in the HPLC profile. It was found that the susceptibility of Lys-6 toward TNBS markedly increased by the addition of Ca2+ when Ca2+ concentration was higher than 5 mM. With regard to the involvement of Lys-6 in the binding of substrate, the increase in the reactivity of Lys-6 may arise from a conformational change around Lys-6 for binding with substrate in the presence of Ca2+. Alternatively, the nonessentiality of Lys-65 for PLA2 activity was revealed by the finding that TNP-1 still retained 95% activity of native enzyme. Moreover, the reactivity of Lys-65 toward TNBS did not greatly change in either the absence or presence of Ca2+, suggesting that Ca2+ binding did not cause an appreciable change in the microenvironment around Lys-65. These results indicate that the differential reactivities of Lys-6 and Lys-65 toward TNBS as affected by the binding of Ca2+ are well consistent with their functional roles in the catalytic mechanism of PLA2, and suggest that the occurrence of conformational changes with PLA2 could be explored by chemical modification studies.

Amino Acid Sequence↗

PubMed1997

The structural variations of epsilon-amino groups in phospholipase A2 enzymes from Naja naja atra and Bungarus multicinctus venoms.

Comparative studies on Naja naja atra phospholipase A2 (NNA-PLA2), Bungarus multicinctus phospholipase A2 (BM-PLA2), and their Lys-modified derivatives were made to assess the differences in the fine structures around the conserved Lys residues of PLA2 enzymes. It has found that the accessibility of Lys residues of PLA2 enzymes toward modified reagent, trinitrobenzene sulfonate, were not the same. Moreover, the extent of decrease in pI values of PLA2 enzymes that resulted from trinitrophenylation of lysine residues was different between NNA-PLA2 and BM-PLA2. The Lys-6 of BM-PLA2 mostly contributed to the positively charged character of the enzyme molecule, whereas the contribution of Lys-6 of NNA-PLA2 to its molecular charge was not notably different from other Lys residues. A linear relationship was observed by plotting the mobilities of PLA2 enzymes and their TNP derivatives against their pI values. However, native and Lys-modified NNA-PLA2 were not aligned with those of BM-PLA2 in the same line. Apparently the gross conformation of PLA2 enzymes was not notably perturbed by the modification of Lys residues, but the fine structure of NNA-PLA2 was not the same as that of BM-PLA2. These results indicate that the positioning of side chains of the conserved Lys residues in the two PLA2 enzymes is essentially different, and suggest that the variations in the fine structures of homologous proteins could be effectively explored by chemical modification studies and electrophoretic analysis.

Amino Acid Sequence↗

PubMed1997

Amino acid sequence and chemical modification of a novel alpha-neurotoxin (Oh-5) from king cobra (Ophiophagus hannah) venom.

A novel alpha-neurotoxin, Oh-5, was isolated from king cobra (Ophiophagus hannah) venom and purified by successive SP-Sephadex C-25 column chromatography and reversed-phase HPLC. The complete sequence of Oh-5 was determined by Edman degradation of peptide fragments generated by endopeptidases, i.e., trypsin, Saccharomyces aureus V8 protease and lysyl endopeptidase. This novel toxin comprises 72 amino acid residues with 10 cysteines. The sequence shows 89% sequence homology with Oh-4, and 60% with Toxins a and b from the same venom. The tyrosine, tryptophan, lysine and arginine residues in Oh-5 were modified with tetranitromethane (TNM), 2-nitrophenylsulfenyl (NPS) chloride, trinitrobenzene sulfonate (TNBS), and p-hydroxyphenylglyoxal (HPG), respectively. Modification of Tyr-4 or Trp-27 did not affect the lethal toxicity at all, while the Tyr-4 and 23 nitrated derivative retained about 50% of the lethality of native toxin. Selective trinitrophenylation of Lys-51 or 69 resulted in a decrease in lethality by 29%, and 50% lethality was retained after modification of Lys-2, 51, and 69. A drastic decrease in lethality to 26% was observed when both Arg-35 and 37 were modified. The neurotoxicity was further decreased when Arg-9 was additionally modified. These results suggest that the aromatic residues, Tyr-4 and Trp-27, are not crucial for the neurotoxicity, whereas the cationic residues are involved in multipoint contact between the toxin molecule and the nicotinic acetylcholine receptor (nAChR). The residues Tyr-23 and Arg-35 and 37 in the central loop of Oh-5 seem to contribute greatly to the neurotoxicity.

Amino Acid Sequence↗

PubMed1997

Heparin-binding epidermal growth factor-like growth factor and transforming growth factor-alpha in human non-small cell lung cancers.

Transforming growth factor-alpha (TGF-alpha), a member of the epidermal growth factor (EGF) family that binds to the EGF receptor (EGFR), is thought to function in an autocrine manner in non-small cell lung cancers (NSCLC). Heparin-binding EGF-like growth factor (HB-EGF), a novel member of the EGF family, also binds to EGFR. To compare the expression of HB-EGF, TGF-alpha and EGFR genes in NSCLC and normal lung tissue, we measured the levels of messenger RNA (mRNA) for these genes in human NSCLC and normal lung tissues by Northern hybridization, reverse transcription-polymerase chain reaction (RT-PCR), and in situ hybridization. A total of eight specimens (paired tumor tissue and normal lung tissue) were harvested from four patients who underwent resection of primary resectable NSCLC. HB-EGF was not expressed in either tumor tissue or normal lung tissue, while EGFR and TGF-alpha were expressed in all samples. TGF-alpha was overexpressed in all tumor tissue samples by several hundred-fold, while the expression of EGFR was not significantly different in tumor tissue and normal lung tissue. There was no correlation between the expression of TGF-alpha and EGFR. In situ hybridization showed that TGF-alpha mRNA was localized mainly in the cancer cells of tumor tissues and in the macrophages of alveoli in normal lung tissue. Our results showed that HB-EGF plays no role in the growth of NSCLC, and that there was no significant overexpression of EGFR in tumor tissue. TGF-alpha may play a major role in the growth of NSCLC. This supports a new direction in rational NSCLC treatment.

Carcinoma, Non-Small-Cell Lung↗

PubMed1997

Rapid identification of mycobacteria to the species level by polymerase chain reaction and restriction enzyme analysis--a case report of corneal ulcer.

We report a case of corneal ulcer caused by nontuberculous mycobacteria which was confirmed by smear and culture. We attempted a new method for the rapid identification of mycobacteria to the species level on the basis of evaluation by the polymerase chain reaction of the gene encoding. The method is involved with restriction enzyme analysis of PCR product obtained with primers common to all mycobacteria. Using the restriction enzyme Bst EII and Hae III, clinically relevant and other frequent laboratory isolates were differentiated to the species or subspecies level by PCR-restriction enzyme analysis. The main prevalence of pattern analysis is Mycobacterium chelonae subsp. abscessus in this case. The outcome suggests that PCR-restriction enzyme analysis should be a useful method for early diagnosis concerning nontuberculous mycobacterial keratitis.

Corneal Ulcer↗

PubMed1996

Ethnic differences in immune responses to hepatitis B vaccine.

A national vaccination program against hepatitis B virus (HBV) to immunize every newborn was initiated in Taiwan in 1986. A serologic survey of 1,812 fully vaccinated children residing in four aboriginal villages and four adjacent nonaboriginal Han Chinese rural villages was conducted in 1993. Children in three of the four aboriginal villages had significantly lower titers of antibody against hepatitis B surface antigen (anti-HBs) than did children in the nonaboriginal villages. Evaluation of cold chain operation for vaccine storage and transport suggested that cold chain failure was not responsible for the fact that children residing in the more remote aboriginal villages had lower mean titers of anti-HBs. However, children whose parents were both aborigines had lower anti-HBs mean titer than did children whose parents were both ethnic Han Chinese. Children of mixed parental origins had intermediate mean titer of anti-HBs. Serologic responses to Japanese encephalitis virus and diphtheria vaccines did not show such correlation with ethnic groups, indicating that the determinant for HBV hyporesponsiveness among the aboriginal children is distinct from that of other childhood vaccines. It was therefore concluded that host factors pertaining to ethnic origin might be responsible for the hyporesponsiveness to HBV vaccine in the aboriginal populations. This finding, if substantiated with further prospective studies, might provide possible means for more targeted trials to improve vaccine response and to reduce vaccine failure among these well-defined ethnic groups.

Child↗

PubMed1996

Chemical modification of cationic residues in toxin a from king cobra (Ophiophagus hannah) venom.

The cationic groups of arginine and lysine residues in alpha-neurotoxin, Toxin a, isolated from king cobra (Ophiophagus hannah) venom were subjected to modification with trinitrobenzene sulfonate (TNBS) and p-hydroxyphenylglyoxal (HPG), respectively. The trinitrophenylated (TNP) derivatives of Toxin a at Lys-10, 56, or 71 showed approximately 25% residual lethality, and modifications on Lys-10 and 56 or Lys-10 and 50 resulted in a decrease of lethality by 84% and 86%, respectively. Modifications on Arg-34, 37, and 70 and Arg-34, 37, and 72 in Toxin a caused a decrease in lethality by 92% and 93%, respectively, and it almost completely lost its lethality and binding activity to nicotinic acetylcholine receptor (nAChR) when all four arginine residues were modified. These results indicate that in addition to the cationic residues on loop II (Arg-34, 37), loop III (Lys-50, 56), and the C-terminal tail (Arg-70, 72; Lys-71), Lys-10 on loop I is also related to the neurotoxicity of Toxin a.

Amino Acid Sequence↗

PubMed1996

The essentiality of calcium ion in the enzymatic activity of Taiwan cobra phospholipase A2.

In order to address the mechanism whereby Ca2+ wad crucial for the manifestation of the enzymatic activity of phospholipase A2 (PLA2), four divalent cations were used to assess their influences on the catalytic activity and the fine structures of Naja naja atra PLA2. It was found that substitution of Mg2+ or Sr2+ for Ca2+ in the substrate solution caused a decrease in the PLA2 activity to 77.5% or 54.5%, respectively, of that in the presence of Ca2+. However, no PLA2 activity was observed with the addition of Ba2+. With the exception of Mg2+, the nonpolarity of the 8-anilinonaphthalene-1-sulfonate (ANS)-binding site of PLA2 markedly increased with the binding of cations to PLA2. In the meantime, the accessibilities of Lys-6 (65) and Tyr-3 (63) toward trinitrobenzene sulfonate and p-nitrobenzenesulfonyl fluoride were enhanced by the addition of Ca2+, Sr2+, and Ba2+, but not by Mg2+. The order of the ability of cations to enhance the ANS fluorescence and the reactivity of Lys and Tyr residues toward modified reagents was Ba2+ > Sr2+ > Ca2+ > Mg2+, which was the same order as the increase in their atomic radii. These results, together with the observations that the ANS molecule binds at the active site of PLA2 and that Tyr-3, Lys-6, and Tyr-63 of PLA2 are involved in the binding with the substrate, suggest that the binding of Ca2+ to PLA2 induces conformational changes at the active site and substrate-binding site. However, the smaller atomic radius with Mg2+ or the bigger atomic radii with Sr2+ and Ba2+ might render the conformation improperly rearranged after their binding to PLA2 molecule.

Anilino Naphthalenesulfonates↗

PubMed1996

Determination of urinary zinc, chromium, and copper in steel production workers.

The aim of our investigation was to determine the concentrations of Cu, Zn, and Cr in urine samples under routine clinical laboratory conditions. To assess the reliability of these methods, critical factors such as detection limit(s), calibration range(s), cost, accuracy, and precision were studied. Our method was employed for the quantitative determination of zinc, chromium, and copper in urine samples from steel production and quality control (QC) workers and healthy unexposed controls. After pretreatment with acids, the samples were digested via a microwave oven. Zinc was determined by flame absorption spectrophotometry (FAAS), whereas chromium and copper were determined by a graphite-furnace atomic absorption spectrophotometry (GFAAS). Our results indicate that urinary zinc, chromium, and copper levels of the exposed workers are significantly higher than those of the controls. The possibility that these metals are involved in the etiology of diseases is discussed and recommendations are made to improve workplace ventilation and industrial hygiene practices.

Calibration↗

PubMed1996

The interaction of 8-anilinonaphthalene-1-sulfonate with His-47 of Taiwan cobra phospholipase A2 perturbing by the binding of calcium ion.

The 8-anilinonaphthalene-1-sulfonate (ANS) fluorescence intensity of ANS-Naja naja atra (Taiwan cobra) phospholipase A2 (PLA2) complex increased with the addition of Ca2+, but the observed fluorescence enhancement markedly decreased after methylation of His-47 in PLA2 molecule. However, the binding affinities of methylated PLA2 for ANS and Ca2+ were similar to or even greater than those observed with native PLA2. These results, together with the finding that ANS electrostatically interacted with His-47 of PLA2, suggest that the increase in the intensity of ANS fluorescence upon the addition of Ca2+, in part, arises from the ionic interaction of His-47 with ANS being perturbed by the binding of Ca2+.

Anilino Naphthalenesulfonates↗

PubMed1996

A significant decrease of the transcriptional activity of p53 mutants deriving from human functional adrenal tumors.

Recently, our laboratory has found a high incidence (77%) of p53 gene mutations in human functional adrenal tumors. Furthermore, the majority of mutant sites were assembled at codons 100, 102, and 249. These mutation sites are not common, and there have been no studies addressing whether or not these mutants points or mutant styles cause the p53 protein to lose function. It has been well known that p53 is a transcription factor. To examine the transcriptional activities of these mutant p53 genes from patients with functional adrenal tumors, we constructed p53 expression plasmids from tumors and paired adjacent normal adrenal gland tissues, using a transient co-transfection assay with a reporter gene in H358 cells. Wild-type p53 from normal adrenal gland tissues specifically trans-activates the expression of a chloramphenicol acetyltransferase (CAT) reporter gene in H358 cells. Three mutant p53 proteins (at codons 100, 102, and 249, respectively) from tumors showed a >90% loss of transcriptional activity. One mutant at codon 68, other than at hot spots, remained at approximately 65% transcriptional activity. An immunoprecipitation assay showed that the mutant proteins of codon 68 and codon 102 could respond to the three monoclonal antibodies (PAbDO-1, PAb1620, and PAb421), indicating that there were no obvious changes in the antigenicity of the proteins. However, the mutant protein of codon 249 could not respond to the carboxy-terminus-specific antibody PAb421 and conformation-specific antibody PAb1620, indicating that there were some obvious changes in the conformation of the mutant proteins. The mutant protein of codon 100 could not be detected by immunoprecipitation assay but could be analyzed by Western blot. In a further study using a DNA-binding assay, it was shown that the loss of transcriptional activity was caused by the loss of DNA-binding ability. These results show that the p53 mutants, derived from functional adrenal tumors, actually lost DNA-binding ability and decreased the transcriptional activity. However, the role of the mutant protein in the tumorigenesis of functional adrenal tumors requires further investigation.

Adrenal Gland Neoplasms↗

PubMed1995

Factor VIII gene inversions in severe hemophilia A: results of an international consortium study.

Twenty-two molecular diagnostic laboratories from 14 countries participated in a consortium study to estimate the impact of Factor VIII gene inversions in severe hemophilia A. A total of 2,093 patients with severe hemophilia A were studied; of those, 740 (35%) had a type 1 (distal) factor VIII inversion, and 140 (7%) showed a type 2 (proximal) inversion. In 25 cases, the molecular analysis showed additional abnormal or polymorphic patterns. Ninety-eight percent of 532 mothers of patients with inversions were carriers of the abnormal factor VIII gene; when only mothers of nonfamilial cases were studied, 9 de novo inversions in maternal germ cells were observed among 225 cases (approximately 1 de novo maternal origin of the inversion in 25 mothers of sporadic cases). When the maternal grandparental origin was examined, the inversions occurred de novo in male germ cells in 69 cases and female germ cells in 1 case. The presence of factor VIII inversions is not a major predisposing factor for the development of factor VIII inhibitors; however, slightly more patients with severe hemophilia A and factor VIII inversions develop inhibitors (130 of 642 [20%]) than patients with severe hemophilia A without inversions (131 of 821 [16%]).

Blotting, Southern↗

PubMed1995

Increased expression of heparin binding epidermal growth-factor-like growth factor mRNA in the kidney of streptozotocin-induced diabetic rats.

Heparin binding epidermal growth factor (HB-EGF), a new member of the EGF family, is a potent mitogen for smooth muscle cells, fibroblasts, and mesangial cells. To study whether the HB-EGF is involved in the development of diabetic nephropathy, we measured the expression of the HB-EGF gene in the kidney tissues of streptozotocin-induced diabetic rats by Northern blot analysis. The mean kidney weight of diabetic rats without strict blood sugar control was significantly increased as compared to that of the control group. Renal HB-EGF mRNA expression was also increased in diabetic rats without strict blood sugar control at 7 days after induction of diabetes and remained elevated for the entire 3-month study period. Strict insulin treatment abolished the elevation of HB-EGF mRNA expression and kidney growth. As HB-EGF is a mitogen for mesangial cells, our results suggest that HB-EGF may be involved in the development of diabetic nephropathy.

Animals↗

PubMed1995

Analysis of a conformation-independent epitope and a conformational epitope in a protein: a study on cobrotoxin from Taiwan cobra venom.

The antibodies against cobrotoxin were separated into two antibody preparations by successive affinity chromatographies on reduced and S-carboxymethylated (RCM)-cobrotoxin-Sepharose, and cobrotoxin-Sepharose columns. The antibodies (abbreviated as Abcf-i) that bound with the RCM-cobrotoxin-Sepharose were verified to specifically recognize the continuous epitopes of cobrotoxin, which were insensitive to conformational changes. Whilst the antibodies (abbreviated as Abcf-d) that did not bind with the RCM-cobrotoxin-Sepharose column recognized the conformational epitopes in cobrotoxin. The two antibody preparations were employed to screen the antigenic peptides derived from the proteolytic hydrolysate of cobrotoxin and RCM-cobrotoxin. Five antigenic peptides (AP-4, AP-5, AP-10, AP-11, and AP-12) were obtained from the acid protease A-digested hydrolysate of cobrotoxin, and two antigenic peptides (V8-2 and V8-4) were found in the hydrolysate of RCM-cobrotoxin after hydrolysis with Saccharomyces aureus V8 protease. The segments at positions 1-21 and 22-38 encompassed the peptide fractions, AP-4, AP-5, V8-2, and V8-4, that reacted with Abcf-i, indicating that the two segments bore the continuous epitopes of cobrotoxin. Alternatively, AP-10, AP-11, and AP-12 reacted with both Abcf-i and Abcf-d. The structures of the three peptides had a common segment at positions 43-62, suggesting that this region comprised the conformation-independent epitopes as well as conformational epitopes in cobrotoxin. These results reflected that the conformation-independent and conformational epitopes in a protein can be separately identified.

Amino Acid Sequence↗

PubMed1995

Chemical modification of cationic groups of a novel alpha-neurotoxin (Oh-4) from king cobra (Ophiophagus hannah) venom.

The cationic groups of arginine and lysine residues in Oh-4, a novel alpha-neurotoxin from king cobra (Ophiophagus hannah) venom were subjected to modification with p-hydroxyphenylglyoxal (HPG) and trinitrobenzene sulfonate (TNBS), respectively. Monoderivatization of Arg-35, resulted in a drastic loss in neurotoxicity to 25% of the native toxin. The activity was decreased to a greater extent with the derivative extensively modified on Arg-35, -9, and -37. The Arg-35-modified derivative retained about a half of the antigenicity of the native toxin, and extensive modification on Arg-9 and Arg-37 caused a further decrease in the antigenicity of the toxin molecule. Selective trinitrophenylation (TNP-) of Lys-51 caused losses of neurotoxicity and antigenicity by 77 and 83%, respectively. These results indicate that Arg-35 and Lys-51 in Oh-4 have important roles in the neurotoxicity. In contrast to the Arg residues at 9, 35, and 37, Lys-51 plays a more critical role in the antigenicity.

Amino Acids↗

PubMed1995

Characterization of epitopes in native and unfolded cobrotoxin: evidence of an immunodominant C-terminal region related to the production of precipitating and non-precipitating antibodies against cobrotoxin.

Rabbits hyperimmunized with cobrotoxin from Taiwan cobra venom produced non-precipitating as well as precipitating antibodies. Both antibody preparations exhibited higher affinity for native cobrotoxin than for reduced and S-carboxymethylated (RCM) cobrotoxin. This indicated that the epitope structures in cobrotoxin are mostly conformation-dependent. In order to identify the conformational epitopes, native cobrotoxin was hydrolyzed with acid protease A, and 12 peptides were obtained on HPLC. Three peptide fragments, AP-10, AP-11, and AP-12, showed pronounced antigenicities toward precipitating as well as non-precipitating antibodies. AP-10, AP-11, and AP-12 contained a common segment in the C-terminal region of cobrotoxin, residues 43 to 62, with intact disulfide linkages. Complete removal of the C-terminal antibodies from antisera and precipitating antibodies on a C-terminal segment-Sepharose affinity column resulted in the loss of their precipitability with cobrotoxin, whilst restoration of precipitability was observed on the addition of the C-terminal antibodies to the C-terminal antibody-depleted antisera and precipitating antibodies. Studies on the antigenic structures of RCM-cobrotoxin revealed that RCM-cobrotoxin contains an immunodominant epitope at positions 22-38. The N-terminal and C-terminal regions of RCM-cobrotoxin encompass other epitopes which exhibit low reactivities toward anti-RCM-cobrotoxin antibodies. However, no precipitated antigen-antibody complexes were observed with the mixture of anti-RCM-cobrotoxin antibodies and RCM-cobrotoxin. These results suggest that the inherently different immunogenicities with different segments might affect the precipitabilities of the resulting antibodies, and that the notable immunogenecity of the C-terminal region is related to the production of precipitating and non-precipitating antibodies against cobrotoxin.

Amino Acid Sequence↗

PubMed1995

Genetic diagnosis of haemophilia A of Chinese origin.

Genetic diagnosis of haemophilia A has been studied in two aspects. One is to directly identify the mutations in the factor VIII genes of the affected probands, and the other is to examine the usefulness of several intragenic factor VIII markers for gene tracking. Direct mutational analysis by PCR-SSCP (polymerase chain reaction--single-strand conformation polymorphism) has been accomplished previously in 87 haemophilia A patients, accounting for nearly 10% of cases in Taiwan. Of the 87 cases, 46% were with point mutations, short deletions or insertions, and most of the remaining were with gene inversion readily identified by Southern blotting. Further examination of 112 patients has estimated a 33% incidence for gene inversion in all the patients with haemophilia A, or 37% in severe cases. Since the direct mutational detection described above cannot be used in all Chinese families with haemophilia A, genetic markers were also investigated. The two CA repeat markers located at intron 13 (CA-13) and intron 22 (CA-22), respectively, were amplified and analysed simultaneously. Seven different alleles with 18-24 CAs have been identified for CA-13. Alleles of 20 and 21 CAs are the most common and their population frequency was 0.68 and 0.24, respectively. The CA-22 marker contained a repetition of (GT)n(AG)n as was identified in the white European but not in the Canadian population. Alleles with 25 and 26 GT/AGs account for 18% and 75% of this group of samples, respectively. The expected rate of heterozygosity for either CA markers was 68%, although a value of 57% was observed by haplotype analysis, indicating an association of the two repeat markers. Nevertheless, the study of 62 females showed that with the combined use of CA-13 and CA-22 with BclI, approximately 71% would be informative for these markers. This number may increase to 81% if XbaI polymorphism is added. We propose that a better genetic diagnosis procedure for Chinese individuals would be first to look for the inversion mutation, secondly for one of the intragenic markers, and then at the PCR-SSCP analysis.

Blotting, Southern↗

PubMed1995

Decrease of renal endothelin 1 content and gene expression in diabetic rats with moderate hyperglycemia.

To investigate the intrarenal endothelin 1 (ET-1) synthesis in streptozocin (STZ) diabetic rats with moderate hyperglycemia, we measured plasma ET-1, renal ET-1 mRNA, and renal tissue ET-1 levels. The renal ET-1 mRNA expression progressively decreased from the 2nd to the 6th week after induction of diabetes by STZ. The renal ET-1 mRNA expression and the renal tissue ET-1 content were significantly reduced in 8 diabetic rats with a mean blood glucose level of 21.0 +/- 0.4 mM as compared with 7 normal rats sacrificed at the 6th week after STZ or citric buffer injection. The reduction of renal ET-1 and mRNA levels was ameliorated in 9 diabetic rats with a mean blood glucose level of 6.9 +/- 0.7 mM after strict glycemic control by insulin treatment. Kidney weight and glomerular filtration rate in moderately hyperglycemic rats were significantly increased as compared with normal rats at the 6th week after STZ injection. The mean plasma ET-1 levels in moderately hyperglycemic diabetic rats were not different from those of the other two groups. This study demonstrates that moderate hyperglycemia in diabetic rats is associated with a reduction in renal ET-1 synthesis. Whether decreased renal ET-1 synthesis is an adaptive phenomenon of a renal hemodynamic change during the early stage of diabetes is worthy of further investigation.

Animals↗