Intestinal absorption of vitamin D sterols: Differential absorption into lymph and portal blood in the rat

Maximo Maislos, Justin Silver, Menahem Fainaru*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

44 Scopus citations

Abstract

Radiolabeled vitamin D sterols (5 nmol) were administered intraduodenally (in fat emulsion) into conscious rats with mesenteric lymph fistula and portal vein cannulation. The rats were kept for 4 h in restraining cages, and lymph and blood samples were collected at half-hour intervals. Vitamin D3 was absorbed mostly into the mesenteric lymph (6.5% of administered dose vs. < 1%/4 h into the portal blood). 1,25-Dihydroxyvitamin D3 was absorbed mainly into the portal blood (~7%/4 h and only 1.6%/4 h into the mesenteric lymph). 25-Hydroxyvitamin D3 had a similar rate of absorption into the lymph and portal vein (5%/4h and 7%/4 h, respectively). Vitamin D3 absorption started after 2 h, whereas the more hydroxylated metabolites were more rapidly absorbed and appeared in the lymph and portal blood within the first half-hour. In the lymph the vitamin D sterols were transported mainly on chylomicrons and lipoproteins (> 50%), whereas in blood less than 20% were associated with plasma lipoproteins. In rats where lymph was not diverted, the increment of lymphatic contribution was observed in plasma levels for all vitamin D sterols. The absorbed sterols in lymph and blood were mostly unchanged with the exception of 25-hydroxyvitamin D3, about one-third of which underwent esterification during absorption into the mesenteric lymph. We conclude that 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3, in particular, are absorbed directly into portal blood independent of fat absorption, and thus may be prescribed as oral supplements in most patients with fat malabsorption.

Original languageEnglish
Pages (from-to)1528-1534
Number of pages7
JournalGastroenterology
Volume80
Issue number6
DOIs
StatePublished - Jun 1981
Externally publishedYes

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