Molecular cloning and expression of inducible nitric oxide synthase in chick embryonic ventricular myocytes.
OBJECTIVE
Inducible nitric oxide synthase (iNOS) has been implicated to contribute to myocardial dysfunction in various settings, but considerable species differences have been noted in the levels of iNOS expression and its function in several tissues. The aim of this study was to elucidate evolutional changes in myocardial iNOS expression and function.


METHODS
An iNOS cDNA clone was isolated by RT-PCR from the 10-day old cultured chick embryonic ventricular myocytes stimulated with 10 micrograms/ml of lipopolysaccharide. Expression of the iNOS mRNA was analyzed with Northern blot analysis and RNase protection assay. The iNOS activity was estimated from conversion rates of L-arginine to L-citrulline and intracellular cGMP contents were measured with radioimmunoassay. Furthermore, both [Ca2+]i (fluorescent dye indo-1) and cell contraction (video motion detector) were simultaneously recorded.


RESULTS
Aside from the primer sequences, the insert (1026 bp) of the cDNA clone showed 66.4% identity at the deduced amino acid level to the human iNOS cDNAs. Northern blot analysis revealed that chicken iNOS mRNA of approximately 4.5 kb was induced by lipopolysaccharide within 6 h in the cultured myocytes. RNase protection assay also showed that lipopolysaccharide provoked 14.6 +/- 5.1-fold increases (n = 6, p < 0.05) in the iNOS mRNA signals within 6 h. The iNOS activity (+300%, P < 0.05) as well as the intracellular cGMP contents (+75%, P < 0.01) were significantly augmented in the lipopolysaccharide-stimulated cells. Both the cell contraction and [Ca2+]i were significantly reduced after the administration of a large amount (10 mM) of L-arginine in the myocytes pretreated with both lipopolysaccharide and NG-monomethyl-L-arginine (100 microM).


CONCLUSIONS
As like as the nucleotide and amino acid sequences, the myocardial effects of the iNOS may also be evolutionary conserved.
Second Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
T
T
Shimizu
K
K
Kinugawa
Y
Y
Sugishita
K
K
Sugishita
K
K
Harada
H
H
Matsui
O
O
Kohmoto
T
T
Serizawa
T
T
Takahashi
D000595:Amino Acid Sequence; D000818:Animals; D001120:Arginine / Q000494:pharmacology; D015152:Blotting, Northern; D002118:Calcium / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D002642:Chick Embryo; D003001:Cloning, Molecular; D017124:Conserved Sequence; D006152:Cyclic GMP / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D006801:Humans; D008070:Lipopolysaccharides; D008969:Molecular Sequence Data; D009200:Myocardial Contraction; D009206:Myocardium / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000037:antagonists & inhibitors / Q000235:genetics*; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000032:analysis; D017386:Sequence Homology, Amino Acid; D019323:omega-N-Methylarginine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D019323:omega-N-Methylarginine; D001120:Arginine; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D006152:Cyclic GMP; D002118:Calcium