title: Calcitroic acid, end product of renal metabolism of 1,25-dihydroxyvitamin D3 through C-24 oxidation pathway.
abstract: About a decade ago calcitroic acid was isolated as a major side chain cleaved water-soluble metabolite of 1,25-dihydroxyvitamin D3 [Esvelt, R. P., Schnoes, H. K., & Decula, H. F. (1979) Biochemistry 18, 3977]. Presently, calcitroic acid is being considered as the major excretory form of 1,25-dihydroxyvitamin D3. However, the exact site or sites of calcitroic acid production and the possible side chain modified intermediary metabolites that may be formed during the conversion of 1,25-dihydroxyvitamin D3 into calcitroic acid are not fully understood. In the mean time there have been many advances in our understanding of the side-chain metabolism of 1,25-dihydroxyvitamin D3. It is now well established that both the kidney and the intestine metabolize 1,25-dihydroxyvitamin D3 through the C-24 oxidation pathway according to the following steps: 1,25-dihydroxyvitamin D3----1,24,25-trihydroxyvitamin D3----1,25-dihydroxy-24-oxovitamin D3-----1,23,25-trihydroxy-24-oxovitamin D3. Recently, we identified 1,23-dihydroxy-24,25,26,27-tetranorvitamin D3 (C-23 alcohol) as a major side chain cleaved lipid-soluble metabolite of 1,25-dihydroxyvitamin D3 and further extended the aforementioned C-24 oxidation pathway in the kidney by demonstrating 1,23,25-trihydroxy-24-oxovitamin D3 as the precursor of C-23 alcohol [Reddy, G. S., Tserng, K. Y., Thomas, B. R., Dayal, R., & Norman, A. W. (1987) Biochemistry 26, 324]. In this present study, we investigated the metabolic fate of 1,25-dihydroxyvitamin D3 (3 X 10(-10) M) in the perfused rat kidney and identified calcitroic acid as the major water-soluble metabolite of 1,25-dihydroxyvitamin D3.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pediatrics, Boston University School of Medicine, Massachusetts 02118.
authors.forename: G S
authors.initials: GS
authors.lastname: Reddy
authors.forename: K Y
authors.initials: KY
authors.lastname: Tserng
mesh_terms: D000818:Animals; D001711:Biotransformation; D002117:Calcitriol / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism*; D008297:Male; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: C021640:calcitroic acid; D002117:Calcitriol