Acute effect of oral, intraperitoneal, and intravenous 1{alpha}-hydroxycholecalciferol on markers of bone metabolism

OBJECTIVE: To study the acute effect of 1-hydoxycholecalciferol (1-OHD₃)on serum levels of alkaline phosphatase, Ca²⁺, osteocalcin,parathyroid hormone (PTH), phosphate and type I and III procollagens(PICP and PIIINP respectively) in patients undergoing peritonealdialysis. Also, 1,25-(OH)₂D₃ was measured. DESIGN: Single doses of 1-OHD₃ (80 ng/kg body wt) were given in randomizedcross-over fashion, orally, intraperitoneally (i.p.) and intravenously(i.v.) on three occasions. Blood was sampled at 0, 1, 6, 12,and 24 h after administration of 1-OHD₃. MAIN RESULTS: Following oral administration of 1-OHD₃, a decrease in serumalkaline phosphatase was seen when levels at 1 and 6 h werecompared to baseline (P<0.05). Oral and i.v. drug administrationsresulted in an increasing trend in serum Ca²⁺ throughout thestudy (P<0.05). Moreover, a difference in serum Ca²⁺ wasfound when 24-h levels after oral 1-OHD₃ dose was compared tobaseline (P<0.05). Serum osteocalcin at 12 and 24 h afteroral 1-OHD₃ compared to baseline were increased (P<0.05).Intact PTH followed a circadian rhythm after all three routesof drug delivery. After 24 h, significant decreases of intactPTH were observed in the oral and i.v. group. No changes inserum phosphate and serum PICP levels were observed over timeafter oral, i.p., and i.v. delivery of 1-OHD₃However, serumPIIINP following oral and i.p. administration of 1-OHD₃ decreasedat 1 and 6 h (P<0.05). CONCLUSION: Oral and iv. administration of 1-OHD₃ does influence serum levelsof osteocalcin, PTH, and PIINP. Noticeable is the significantincrease in serum osteocalcin after oral administration of 1-OHD₃,the remarkable increase (22.6%) in osteocalcin 24 h after i.v.1-OHD₃, though not statistically significant, the increase inserum PTH levels 12 h following oral and i.v. doses of 1-OHD₃and the moderate effect on serum Ca²⁺ levels.