Cell engraftment is a new strategy for the repair of ischemic myocardial lesions. The hemodynamic effectiveness of this strategy, however, is not completely elucidated yet. In a rat model of cryothermia-induced myocardial dysfunction, we investigated whether syngeneic transplantation of neonatal cardiomyocytes or satellite cells is able to improve left ventricular performance. Myocardial infarction was induced in female Lewis rats by a standardized cryolesion to the obtuse margin of the left ventricle. After 4 weeks, 5 x 10(6) genetically male neonatal cardiomyocytes (n = 16) or satellite cells (n = 16) were engrafted into the myocardial scar. Sham-transplanted animals (n = 15) received injections with cell-free medium. Sham-operated animals (n = 15) served as controls. Left ventricular performance was analyzed 4 months after cell engraftment. Chimerism after this sex-mismatched transplantation was evaluated by detection of PCR-amplified DNA of the Y chromosome. The average heart weight of the infarcted animals significantly exceeded that of controls (p < 0.05). In sham-transplanted animals, mean aortic pressure, left ventricular systolic pressure, aortic flow (indicator of cardiac output), and left ventricular systolic reserve were significantly lower (p < 0.05) compared with sham-operated controls. This was associated with deterioration of ventricular diastolic function (maximal negative dP/dt, time constants of isovolumic relaxation; p < 0.05). Transplantation of satellite cells was found more effective than transplantation of neonatal cardiomyocytes, resulting in i) normalization of mean aortic pressure compared with sham-operated controls, and ii) significantly improved left ventricular systolic pressure and aortic flow (p < 0.05) compared with sham-transplanted animals. Left ventricular systolic reserve and diastolic function, however, were improved by neither satellite cell nor neonatal cardiomyocyte transplantation. Analysis of male genomic DNA revealed 3.98 +/- 2.70 ng in hearts after neonatal cardiomyocyte engraftment and 6.16 +/- 4.05 ng in hearts after satellite cell engraftment, representing approximately 10(3) viable engrafted cells per heart. Our study demonstrates i) long-term survival of both neonatal cardiomyocytes and satellite cells after transplantation into cryoinfarcted rat hearts, ii) slight superiority of satellite cells over neonatal cardiomyocytes in improving global left ventricular pump performance, and iii) no effect of both transplant procedures on diastolic dysfunction.