Calcitriol synthesis is decreased in spontaneously hypertensive rats

• Published in: Kidney international Vol. 34; no. 2; pp. 224 - 228
• Main Authors: Patel, Sanjeev, Simpson, Robert U., Hsu, Chen H.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.08.1988; Nature Publishing
• Subjects: Aging - metabolism; Animals; Biological and medical sciences; Calcitriol - biosynthesis; Calcium - metabolism; Creatinine - metabolism; Hypertension - metabolism; Male; Medical sciences; Metabolic Clearance Rate; Nephrology. Urinary tract diseases; Nephropathies. Renovascular diseases. Renal failure; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Renovascular diseases; Hypertension; Vertebrata; Experimental disease; Metabolic disorder; Mammalia; Urinary system disease; Rat; Deficiency; Rodentia; Cardiovascular disease; Biosynthesis
• ISSN: 0085-2538; 1523-1755
• DOI: 10.1038/ki.1988.168

Calcitriol synthesis is decreased in spontaneously hypertensive rats. To investigate the mechanisms of abnormal calcium metabolism, such as hypocalcemia, decreased intestinal calcium absorption and hypercalciuria in spontaneously hypertensive rats (SHR), we have measured the plasma concentration of calcitriol and its synthesis in 5-, 8-, 12-, 16-, and 20-week-old normotensive Wistar Kyoto rats (WKY) and SHR. Metabolic clearance rate (MCR) and production rate (PR) of calcitriol were measured by the constant isotope infusion method. Plasma concentration of calcitriol and PR of calcitriol were decreased in SHR after 12 weeks of age. MCR of calcitriol, however, was not different between WKY and SHR in any age group. Therefore, the decreased synthesis of calcitriol accounts for the lower plasma level of calcitriol in SHR afer 12 weeks of age. Metabolic acidosis or decreased renal function could not account for the decreased synthesis of calcitriol, since the blood pH and pCO2and creatinine clearance were similar between WKY and SHR at times when the calcitriol synthesis was reduced in SHR. Plasma concentration of ionized calcium was also lower in SHR after 12 weeks of age. Plasma concentration of calcitonin was significantly higher in 16-week-old SHR (41.6 ± 1.5 pg/ml) than in age-matched WKY (30.5 ± 1.7, P < 0.001). The values, however, were not different between 8- and 12-week-old WKY and SHR. We believe that the decreased synthesis of calcitriol could be the pathogenetic factor for the development of abnormal calcium metabolism in SHR. Age of animals should be considered when studying the calcium metabolism in SHR.