Obstructive nephropathy caused by a single Intraperitoneal injection of sodium sulfaacetylthiazole (SAT) in a dosage of 0.5 gm/ kg body weight induced interstitial myocarditis and medial calcification with medionecrosis of the aorta in 4-month-old rats but not in immature I·month·old rats. The calcium content of the aorta, heart and kidneys and the 24·hour uptake of 4GCa by the aorta, heart and kidneys were signifi. cantly increased. The histological changes, the increased calcium content of the heart and aorta, and the increased uptake of 45Ca were prevented by prior parathyroidectomy. Inteaoseeous 45Ca two weeks after administration for the purpose of labelUng the stable bone fraction, was markedly decreased by injection of SAT in rats above the age of 4 months with intact parathyroids but not in immature rats and in parathyroidectomized adult animals. Such mobilization of 4GCa in the stable bone fraction was probably promoted through the increased secretion of parathyroid hormone secondary to SAT·induced acute renal failure.An increase in the calcium content of the tissues is intimately related to the development of age-related cardiovascular lesions. In 1959 Lehr (1) reported the preventive effect of parathyroidectomy on the cardiovascular changes induced by administration of sodium sulfaacetylthiazole (SAT) and pointed out the importance of calcium metabolism in such changes. Based on our own observations on the importance of both age and calcium metabolism in such cardiovascular alterations (2), we used 4 G Ca for the study of the dynamic aspects of this calcium metabolism in more detail.
MATERIALS AND METHODSNinety-eight male rats of the Wistar strain, at the ages of approximately 4 months and 1 month and weighing 30D--400 gm and 80-100 gm respectively, were maintained with Oriental Rat Chow (calcium content 1.85 per cent) and tap water ad libitum. Some animals were parathyroidectomized by hot-wire cautery