Induction of cell-cycle inhibitor p21 in rat ventricular myocytes during early postnatal transition from hyperplasia to hypertrophy.
To examine a possible involvement of p21 protein, an inhibitor of cyclin-dependent kinases (CDKs), in the transition from hyperplastic to hypertrophic growth of rat ventricular myocytes during the first postnatal week, we analysed day-by-day changes in the number of p21 positive cells using specific antibodies against this protein. Paraffin-embedded sections of the left ventricular myocardium were examined by means of immunoperoxidase technique and hematoxylin-eosin counterstaining. While during the first three postnatal days, the positive reaction for p21 was detected only in a small fraction of myocytes (12-20%), a sudden increase in positivity occurred on day 4 (54%) and continued till day 6 when the fraction of cells expressing p21 reached 87%. Our results show that the induction of CDK inhibitor p21 in rat ventricular myocytes is developmentally regulated. Moreover, the fact that the sudden increase in p21 positivity occurred at the same stage when the myocyte proliferation rapidly ceases, suggests that this protein is likely to be involved in mediating this key event of cardiac development.
Horký
M
M
Department of Pathological Physiology, Masaryk University, Brno, Czech Republic.
Kuchtícková
S
S
Vojtesek
B
B
Kolár
F
F
D000375:Aging; D000818:Animals; D000831:Animals, Newborn; D002455:Cell Division; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D016213:Cyclins / Q000096:biosynthesis*; D004791:Enzyme Inhibitors; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
C493958:Cdkn1a protein, rat; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D018844:Cyclin-Dependent Kinases