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

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.

Response of the Rat Heart to Bilateral Ovariectomy and Estrogen

BACKGROUND AND OBJECTIVES: Although ovarian estrogen is believed to decrease coronary heart disease by improving plasma lipoprotein and enhancing vasodilation, estrogen effect on heart tissue has not been shown yet. So we investigated the effect of the ovariectomy and estrogen on rat heart tissue. MATERIALS AND METHODS: Female Sprague Dawley rats, about 3 months of age, were subjected to sham surgery (n=9) or bilateral ovariectomy (n=20) and maintained untreated for 8 weeks after surgery. We administered estrogen (20 mg/Kg subcutaneously, 3 times/week) to 10 ovariectomized rats for 4weeks; the remaining ovariectmized rats received only saline. Animals were divided in 3 group:group 1 (control); sham op, group 2; ovariectomized only, group 3; ovariectomy+estrogen. We measured left ventricular thickness [IVS+LVPW)/2] and number of cardiomyocytes and interstitial fibrosis on light microscope (H & E and Masson's trochrome stain) and electron microscope. RESULTS: 1) LV wall thicknesses were significantly increased in group 2 and group 3 as compared with group 1 (2.45+/-0.1 and 2.46+/-0.11 vs 2.31+/-0.15 mm). 2) There were no significant change in the number of cardiomyocyte between group 1, group 2 and group 3 (54.3+/-5.7, 60.2+/-19.4, 52.5+/-14.1). 3) Group 2 and group 3 show more interstitial edema (44% and 62.5% vs 0%) on LM and more interstitial edema and the increase of number of mitochondria on EM than group 1. CONCLUSION: Bilateral ovariectomized rats show the increase of LV wall thickness, which was caused by interstitial edema without cardomyocyte hypertrophy and these changes were not reversed by the short-term administration of estrogen for 4 weeks.