Involvement of receptor-type tyrosine kinase gene families in cardiac hypertrophy.
OBJECTIVE
The activation of protein tyrosine kinases (PTKs) has been postulated to be involved in cell differentiation and proliferation. To elucidate the involvement of tyrosine kinase genes in normal and pathological conditions, we analysed the expression patterns of receptor-type PTKs in the normal and hypertensive hypertrophied heart in rats.


METHODS
Hypertrophied and normal rat hearts were obtained from hypertensive rats; deoxycorticosterone acetate (DOCA)-salt and 2 kidney-1 clip (2K-1C), and their sham-operated rats, respectively. A reverse transcription-polymerase chain reaction (RT-PCR) was performed using degenerated primers which were designed from highly conserved regions in the catalytic domains of receptor-type PTKs. The PCR products were ligated into a sequence vector, and subcloned by transforming bacteria. To compare the expression level of these PTK mRNAs in the normal and hypertrophied heart, we performed semi-competetive RT-PCR and immunohistochemical and Western blot analyses.


RESULTS
Nucleotide sequencing of approximately 80 clones of PTKs revealed 10 receptor-type, five nonreceptor-type and two unknown types in the rat heart. Tie-2/Tek, Ryk, insulin-like growth factor-I receptor were abundantly expressed in the rat heart as members of receptor-type PTKs. Immunohistochemistry and RT-PCR demonstrated the presence of platelet-derived growth factor (PDGF)-alpha receptor, PDGF-beta receptor and fibroblast growth factor-3 receptor in both normal and hypertrophied hearts. We also confirmed the presence of Flt-1, KDR/FIk-1, and their ligand vascular endothelial growth factor, c-Met and its ligand hepatocyte growth factor (HGF), and Tie-1, Tie-2/Tek by immunohistochemistry and RT-PCR. The coexpression of cardiac HGF and c-Met in hypertrophied hearts, especially in 2K-1 C rats, was induced more intensively than that in DOCA-salt rats.


CONCLUSIONS
These findings suggest that HGF/c-Met interactions may play an important role in cardiac hypertrophy and remodeling, probably as a result of the activation of the local renin-angiotensin system.
Akiyama
Y
Y
Third Department of Internal Medicine, Atomic Bomb Disease Institute, Nagasaki University School of Medicine, Nagasaki City, Japan.
Ashizawa
N
N
Seto
S
S
Ohtsuru
A
A
Kuroda
H
H
Ito
M
M
Yamashita
S
S
Yano
K
K
D000818:Animals; D015153:Blotting, Western; D006332:Cardiomegaly / Q000201:enzymology* / Q000209:etiology / Q000235:genetics*; D020134:Catalytic Domain / Q000235:genetics; D003001:Cloning, Molecular; D017124:Conserved Sequence / Q000235:genetics; D017228:Hepatocyte Growth Factor / Q000235:genetics; D006973:Hypertension / Q000150:complications; D007150:Immunohistochemistry; D008297:Male; D008969:Molecular Sequence Data; D005810:Multigene Family; D019859:Proto-Oncogene Proteins c-met / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
D017228:Hepatocyte Growth Factor; D019859:Proto-Oncogene Proteins c-met; D020794:Receptor Protein-Tyrosine Kinases