Localization of c-myc protooncogene expression in the rat heart in vivo and in the isolated, perfused heart following treatment with norepinephrine.
We have investigated the expression of the protooncogene c-myc in rat hearts following exposure to norepinephrine, both in vivo and in isolated perfused preparations. Both chronic and acute norepinephrine treatment produced a rapid, transient elevation of c-myc mRNA in adult rat hearts, but chronic infusion produced a second, larger increase. This expression profile was characteristic for c-myc since it was not found for four other protooncogenes. In the isolated, perfused heart, addition of norepinephrine to the perfusion buffer and elevation of perfusion pressure separately increase c-myc mRNA suggesting both direct hormonal and hemodynamic factors might be important in vivo. Immunocytochemistry showed that Myc protein accumulated predominantly in the nuclei of non-myocyte cells following norepinephrine treatment indicating that expression at the mRNA level culminated in protein synthesis. These findings suggest that the c-myc expression observed in the hypertrophying adult heart following exposure to norepinephrine may be associated with proliferating cells like fibroblasts rather than cardiomyocytes.
Hannan
R D
RD
Department of Biochemistry, University of Tasmania, Hobart, Australia.
Stennard
F A
FA
West
A K
AK
D000818:Animals; D015870:Gene Expression; D006321:Heart / Q000187:drug effects*; D007150:Immunohistochemistry; D008297:Male; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D009638:Norepinephrine / Q000494:pharmacology*; D010477:Perfusion; D011312:Pressure; D016271:Proto-Oncogene Proteins c-myc / Q000032:analysis*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar
D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D009638:Norepinephrine