Injection of 1,25-(OH)2 Vitamin D3 Enhances Resistance Artery Contractile Properties

• Published in: Hypertension (Dallas, Tex. 1979) Tex. 1979), 1990-11, Vol.16 (5), p.523-531
• Main Authors: Bukoski, Richard D, Wang, Dabao, Wagman, D Wolfe
• Format: Article
• Language: English
• Subjects: Animals; Calcitriol - pharmacology; Calcium - metabolism; Endothelium, Vascular - drug effects; Male; Myocardial Contraction - drug effects; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Vascular Resistance - drug effects; Vasoconstriction - drug effects
• ISSN: 0194-911X; 1524-4563
• DOI: 10.1161/01.hyp.16.5.523

The hypothesis that 1,25-dihydroxyvitamin D3 [l,25-(OH)2 vitamin D3] modulates vascular smooth muscle contractile function was tested. 1,25-(OH)2 vitamin D3 (50 ng/day) was administered by intraperitoneal injection over a 3-day period to 13–15-week-old male spontaneously hypertensive and Wistar-Kyoto normotensive rats. On the fourth day, serum was prepared and contractile force generation of isolated mesenteric resistance arteries was examined. Treatment with 1,25-(OH)2 vitamin D3 approximately doubled serum levels of the hormone and increased ionized and total serum Ca and phosphate by 5–10%. No effect on blood pressure was detected. 1,25-(OH)2 vitamin D3 injection in both strains enhanced maximal stress generation to norepinephrine and serotonin by 30–40%, with no effect on apparent sensitivity of the vessels to the agonists. To assess the effect of a maneuver that elevates serum ionized Ca without the addition of exogenous hormone, maximal stress generation was examined in resistance arteries isolated from rats fed diets containing 0.5% or 2% calcium over a 6–7-week period. Maximal stress generation in response to norepinephrine was greater in vessels from rats of both strains maintained on 0.5% calcium. It is concluded that 72-hour in vivo treatment with 1,25-(OH)2 vitamin D3 increases contractile force-generating capacity of resistance arteries without affecting blood pressure. It is proposed that this action of 1,25-(OH)2 vitamin D3 is the result of a direct action of the hormone on the vascular wall.