Effect of Parathyroid Hormone on Left Ventricular Hypertrophy in Aged Ovariectomized Rats

ABSTRACT

BACKGROUND: It has been well known that the bone and kidney are the principle organs of parathyroid hormine (PTH) actions. Although patients with primary hyperparathyroidism show a high incidence of LVH and trophic effects of PTH on adult rat ventricular cardiomyocytes were investigated in vitro, effect of PTH on the cardiac tissue in vivo is unknown. METHODS: We examined the effects of PTH on the cardiomyocyte and interstitial tissue using adult rat heart. Twenty-two female Sprague-Dawley rats were ovariectomized bilaterally at three months old and weighing in 250 - 300 gm in order to exclude the trophic effect of estrogen. We administrated human parathyroid hormone (20 ug subcutaneously 5 times per week) to 12 rats for 4 weeks after raising for 8 weeks (PTH group)the remaining 10 rats received only normal saline (control). We measured left ventricular thickness [IVS+LVPW)/2] and number of cardiomyocytes and interstitial fibrosis on LM (H & E and Masson's trochrome stain) and EM. RESULTS: 1) LV wall thickeness tended to increase in PTH group as compared with control (2.16+/-0.31 vs 1.12+/-0.21 mm, p=0.099). 2) The number of cardiomyocyte in PTH group was significantly less than that of control (61.2+/-13.1 vs 70.5+/-14.9, p=0.003, Magnification x 400). 3) There was no significant change of interstitial fibrosis between PTH group and control. CONCLUSION: These results shggest that PTH may produce left ventricular hypertrophic effects in aged ovariectomized rat that resulted form hypertrophy of cardiomyocyte without increase of interstitial connetive tissue.