Hypertrophied myocardium is more dependent on extracellular calcium than the normal cardiac muscle.
BACKGROUND
The aim of this study was to analyze stable hypertrophied myocardial function and its response to inotropic maneuvers in rats submitted to renovascular hypertension for a 10-week period (RHT group, n=10).


METHODS
Myocardial performance was studied in isolated left ventricle papillary muscles in isometric contraction under the following conditions: at postrest contraction of 30 seconds (PRC), at extracellular calcium (ECa2+) chloride concentration of 1.25 and 5.20 mM, and after beta-adrenergic stimulation with 10-6 M isoproterenol (ISOP).


RESULTS
The results were compared with normotensive Wistar controls rats (C group, n=10). In basal condition, resting tension, and contraction time (TPT) were greater, while relaxation time (RT50) tended to be longer in RHT than C group. PRC and ISOP promoted a similar change in muscle function response intensity (delta) in both groups. ECa2+ shift did not change TPT in the C group and decreased TPT in the RHT animals; delta was different between these groups. RT50 increased in C and decreased in RHT, both without statistical significance; however, delta was different.


CONCLUSIONS
These results suggest that hypertrophied myocardial dysfunction may be attributed to changes in intracellular calcium cycling.
de Barros
Reginaldo
R
Botucatu Medical School, UNESP-São Paulo State University, Botucatu, Brazil.
Zornoff
Leonardo A M
LA
Ribeiro
Henrique B
HB
Okoshi
Marina P
MP
Padovani
Carlos R
CR
Aragon
Flavio F
FF
Cicogna
Antonio C
AC
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism*; D006984:Hypertrophy; D007537:Isometric Contraction / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology*; D051381:Rats; D017208:Rats, Wistar; D012146:Rest / Q000502:physiology; D013599:Systole / Q000187:drug effects
D007545:Isoproterenol; D002118:Calcium