Studies on the Calcium Metabolism of the Cardiovascular System in Acute Renal Injury

I. Studies on the Pathogenesis of the Cardiovascular Changes Induced by Na-Sulfacetylthiazole

Abstract

A single intraperitoneal administration of Na-Sulf-acetylthiazole (SAT), 0.5g/kg body weight as 5% aqueous solution into rats caused interstitial nephritis leading to obstructive nephropathy, which induced medionecrosis with medial calcification of the aorta, interstitial myocarditis and nephrocalcinosis in rats above the age of 4 months but not in 40 day old immature animals. Calcium content of the aorta, heart and kidneys and 24hrs. uptake of ⁴⁵Ca by those organs 3 days after. SAT treatment were significantly increased in adult rats. Microautoradiogram of the aorta showed the localization of the grains of ⁴⁵Ca in the media in correspondence to the histological findings. In the microautoradiogram of the kidney, the grains of Ca aggregated in the tubular canals and in the tubular epithels, and also scattered in the degenerated interstitial tissues but not in the foci of the cell infiltration without degenerative changes. Such histological changes and increase of the calcium content and 24hrs. uptake of ⁴⁵Ca by the heart and aorta were prevented by prior parathyroidectomy. The content of ⁴⁵Ca administered 2 weeks before SAT treatment to label the stable fration of the femur was markedly decreased in response to the administration of SAT in intact adult rats but not in immature or parathyroidectomized adult animals. These changes in calcium metabolism are probably due to the increased parathyroid hormone activity secondary to ranal injury. The greater susceptibility of older rats to SAT-induced cardiovascular changes than younger ones might be due to the increased avidity of soft tissues to calcium salts.