Human Troponin T & I (TnT, TnI) has several isoforms which have different functional property. This study was designed to describe the isoform expression of TnT & TnI in failing and hypertrophic human heart and during normal development.

Myocardium was attained from hypertrophic hearts (N=10) of TOF patients who underwent myomectomy, from failing hearts (N=10) of transplant recipients, from normal hearts (N=5) of patients in brain death and from aborted fetal hearts (N=5). After the extraction of RNA, RT-PCR was performed for TnT & TnI isoforms and GAPDH to evaluate the isoform expression qualitatively and quantitatively.

In terms of TnI, slow skeletal TnI was expressed more than cardiac TnI in fetal hearts[ratio of Troponin over GAPDH (R)=1.3 : 0.5] but cardiac TnI was dominant in adult hearts (R=0.3 : 1.1) (p<0.05). Failing hearts showed similar pattern with adult hearts (R=0.3 : 1.2) and hypertrophic hearts showed the intermediate pattern (R=0.9 : 1.3). In terms of TnT, T1 and T3 were expressed in fetal hearts (R=0.04, 0.8) but only T3 was expressed in adult hearts (R=1.1). Failing hearts and hypertrophic hearts showed similar pattern with adult hearts and no differences in the amount of expression (R=1.4, 1.3).

There is isoform switch from fetal to adult form during development and it might be responsible for the differences of myocardial functional property between fetal and adult heart. Failing and hypertrophic hearts showed no differences with normal hearts, which means the isoform switch of TnT & I might have no significant role in functional disturbances in these conditions.