Influence of aging and long-term swimming exercise on parvalbumin distribution in rat hearts

Parvalbumin (PV), which is a small (12kDa) cytoplasmic calcium-binding protein, has been implicated in mediating relaxation in cardiac myocytes. The influence of aging and exercise on the distribution of PV in rat heart was investigated. Male Wistar rats aged 3, 6, 12 and 18-months were divided into sedentary and exercise groups. The exercise group underwent exercise in the form of regular swimming for 6 months. The hearts were processed for immunohistochemistry and Western blotting. The intensity of PV immunoreactivity was strong in the 9 and 12-month hearts and decreased in the 18-month hearts. The smallest amount was detected in the 24-month rat hearts when compared to those of the 9, 12 and 18-month rat hearts. Significantly less PV was detected in the 18 and 24-month hearts compared to the 12-month rat hearts (P<0.05). The intensity of PV immunoreactivity was considerably stronger in hearts of the 9, 12 and 18-months exercised rats than in hearts of age-matched sedentary rats. However, in the hearts of 24-month rats, immunoreactivity was only slightly stronger in the exercised rats in comparison with those of sedentary rats. A significant increase of PV detection in hearts was found in the exercised rats in comparison with sedentary rats in the 9 (P<0.05) and 18-month samples (P<0.01). Our data indicate that PV is down-regulated in the rat heart during aging. In addition, our data indicate that long-term swimming exercise could induce an increase of PV expression.