Effect of Intermittent Versus Continuous Parathyroid Hormone in the Cardiovascular System of Rats

OBJECTIVE: PTH increases ionic calcium concentration in the serum, acting primarily on bone and kidney cells through the type 1 PTH receptor. Interestingly, PTH stimulates bone formation when administrated intermittently but causes severe bone loss with continuous administration. Daily injections of PTH are used as the most promising anabolic agent in the treatment of severe osteoporosis. Elevated PTH is reported an independent risk factor for left ventricle hypertrophy. DESIGN: in rats we investigated the effect of intermittent and continuous administration of PTH on blood pressure, heart rate and development of cardiac hypertrophy and fibrosis. RESULTS: We did not find PTH to induce heart hypertrophy. In contrast, continuous administration of PTH the mRNA level of a hypertrophic marker gene, atrial natriuretic peptide. When comparing the effect of continuously versus injected PTH collagen 1 mRNA was significantly higher in continuously treated animals. CONCLUSION: our data demonstrated a decrease in heart rate upon continuous administration of PTH in rats. No changes in blood pressure were observed. Moreover, neither intermittent nor continuous administration of PTH induced ventricular hypertrophy. But continuous PTH induced a marker of collagen 1. Thus, these data did not reveal any negative effects of the injection of PTH on the cardiovascular system.