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United States Department of Agriculture

Agricultural Research Service

Title: REFINEMENT OF RETINYL PALMITATE ASSAY REVEALS EARLIER ASSAYS GROSSLY OVERESTIMATE CONCENTRATIONS IN PLASMA)

Author
item Zimmerman, Duane
item Horst, Ronald
item Goff, Jesse
item Hoy, Derrel
item Beitz, Donald

Submitted to: American Dairy Science Association Abstracts
Publication Type: Abstract only
Publication Acceptance Date: 7/25/1998
Publication Date: N/A
Citation:

Interpretive Summary:

Technical Abstract: Vitamin A status in dairy cows has been determined by plasma concentrations of retinol and retinyl palmitate or retinyl palmitate alone, as analyzed by HPLC from a single column assay. Using this type of analytical system, concentrations of retinyl palmitate as high as 750 ng/mL have been reported. Retinol concentrations in plasma range from 150 ng/mL to 250 ng/mL in normal dairy cows. Unfortunately, the alleged retinyl palmitate peak included other compounds in addition to the retinyl palmitate. We recently developed a quantitative assay for retinol and retinyl palmitate which utilizes a 2-column system, resolving retinyl palmitate from other coeluting solutes. The retinyl palmitate peak collected from the first HPLC column was then applied to a C18 column with a mobile phase of 75:20:5 (v:v:v) methanol:chloroform:water. As a test of this new assay for retinyl palmitate and retinol, 10 nonlactating, nonpregnant Jersey cows were assigned randomly to 1 of 3 oral daily treatments of retinyl palmitate for 14 d: 0; 125,000 IU; or 250,000 IU. Retinyl palmitate concentrations in plasma collected during the 14 d ranged from undetectable to 9 ng/mL without dosing and from undetectable to 9 ng/mL with both doses of retinyl palmitate. Retinol concentrations ranged from 180-230 ng/mL without dosing and 225-285 ng/mL with both doses of retinyl palmitate. Retinyl palmitate concentrations of 10 ng/mL are an insignificant proportion of total circulating retinoids since retinol concentrations are normally around 250 ng/mL. Therefore, using retinyl palmitate concentrations in plasma as a diagnostic tool for vitamin A status in dairy cows seems inappropriate.

Last Modified: 8/24/2016
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