Injection of 1,25-(OH)2 vitamin D3 enhances resistance artery contractile properties.
The hypothesis that 1,25-dihydroxyvitamin D3 [1,25-(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 Ca2+ 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 Ca2+ 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.
Bukoski
R D
RD
Department of Medicine, Oregon Health Sciences University, Portland 97201.
Wang
D B
DB
Wagman
D W
DW
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D014655:Vascular Resistance / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects*
D002117:Calcitriol; D002118:Calcium