ACUTE EFFECT OF ORAL, INTRAPERITONEAL, AND INTRAVENOUS 1-ALPHA-HYDROXYCHOLECALCIFEROL ON MARKERS OF BONE METABOLISM

Objective. To study the acute effect of 1alpha-hydoxycholecalciferol ( 1alpha-OHD3) on serum levels of alkaline phosphatase, Ca2+, osteocalci n, parathyroid hormone (PTH), phosphate and type I and III procollagen s (PICP and PIIINP respectively) in patients undergoing peritoneal dia lysis. Also, 1,25-(OH)2D3 was measured. Design. Single doses of 1alpha -OHD3 (80 ng/kg body wt) were given in randomized cross-over fashion, orally, intraperitoneally (i.p.) and intravenously (i.v.) on three occ asions. Blood was sampled at 0, 1, 6, 12, and 24 h after administratio n of 1alpha-OHD3. Main results. Following oral administration of 1alph a-OHD3, a decrease in serum alkaline phosphatase was seen when levels at 1 and 6 h were compared to baseline (P < 0.05). Oral and i.v. drug administrations resulted in an increasing trend in serum Ca2+ througho ut the study (P < 0.05). Moreover, a difference in serum Ca2+ was foun d when 24-h levels after oral 1alpha-OHD3 dose was compared to baselin e (P < 0.05). Serum osteocalcin at 12 and 24 h after oral 1alpha-OHD3 compared to baseline were increased (P < 0.05). Intact PTH followed a circadian rhythm after all three routes of drug delivery. After 24 h, significant decreases of intact PTH were observed in the oral and i.v. group. No changes in serum phosphate and serum PICP levels were obser ved over time after oral, i.p., and i.v. delivery of 1alpha-OHD3. Howe ver, serum PIIINP following oral and i.p. administration of 1alpha-OHD 3 decreased at 1 and 6 h (P < 0.05). Conclusion. Oral and i.v. adminis tration of 1alpha-OHD3 does influence serum levels of osteocalcin, PTH , and PIIINP. Noticeable is the significant increase in serum osteocal cin after oral administration of 1alpha-OHD3, the remarkable increase (22.6/o) in osteocalcin 24 h after i.v. 1alpha-OHD3, though not statis tically significant, the increase in serum PTH levels 12 h following o ral and i.v. doses of 1alpha-OHD3 and the moderate effect on serum Ca2 + levels.