Vitamin A Concentrations in Piglet Extrahepatic Tissues Respond Differently Ten Days after Vitamin A Treatment

Abstract

Periodic supplementation to infants and young children is encouraged in developing countries by the WHO. We investigated vitamin A (VA) in extrahepatic tissues of piglets after supplementation with retinyl acetate to determine long-term storage. 3, 4-Didehydroretinyl acetate (DRA) as a tracer was used to evaluate uptake from chylomicra in 4 h. Sows were fed a VA-depleted diet throughout pregnancy and lactation. Male castrated piglets (n = 28, 11.6 +/- 0.5 d) from these sows were weaned onto a VA-free diet for 1 wk, assigned to 4 groups, and dosed orally with 0, 26.2, 52.4, or 105 micromol VA. After 10 d, 5.3 micromol DRA was administered to determine short-term uptake of 3, 4-didehydroretinol (DR). Four hours later, piglets were killed; adrenal glands, kidney, lung, and spleen were collected and analyzed for retinol and DR. Retinol concentrations of kidney and adrenal gland were higher than control, but treated groups did not differ. Retinol concentration was highest in kidney (1.70-2.52 nmol/g), followed by adrenal gland (0.30-0.48 nmol/g), lung (0.15-0.21 nmol/g), and spleen (0.11-0.15 nmol/g). Total retinol in kidney and spleen was different among the groups (P < 0.05). Unesterified retinol was the major VA form; the percent retinol of total VA was lowest in adrenal glands. DR did not differ among the groups. In 4 h, the minimum estimated chylomicron contribution to tissue DR was 63-280% higher than the maximum DR exposure from retinol-binding protein. Constant dietary intake may be important in maintaining VA concentrations in extrahepatic tissues.

Vitamin A Supplementation Transiently Increases Retinol Concentrations in Extrahepatic Organs of Neonatal Rats Raised under Vitamin A–Marginal Conditions

“…This observation was similar to findings in neonatal piglets, in which the liver ranked as the highest in terms of retinol concentration, followed by the kidneys and lungs, irrespective of VA treatment (23). However, kinetic studies in rats supplemented with VARA have shown a dramatic stimulatory effect of supplementation on the uptake and retention of retinyl esters by the lungs and intestine (14,36), consistent with the previously demonstrated role of retinoic acid in upregulating genes responsible for VA storage (37)(38)(39).…”

“…The liver contained ;76% of the whole-body VA mass in control pups aged 4-8 d, a proportion similar to the 86% of hepatic retinol found in adult rats and humans in the VA-adequate state (21,22). This relatively high proportion of hepatic retinol was maintained despite a liver retinol concentration that was deficient and significantly lower than that measured in adult mother rats fed the VA-marginal diet (Figure 7), a finding consistent with the low neonatal liver retinol concentration found in piglets fed a VA-free diet (;25 nmol/g) and in newborn humans (5,23).…”

Healthy birth weight results in higher vitamin A storage in neonate piglets administered high-dose supplements

“…The retinol values from the high doses of VA would have had more time to equalize with total body retinol in the Sun et al study considering the 10-day wait period before organ harvest. 21 Further, lung retinol concentrations likely peaked earlier than 12 h in the current study considering that the first pass of chylomicron-delivered VA, which deliver large amounts to the lung, 19,21,29 would have cleared before 12 h.…”

“…27 The rank of VA concentration in organs analyzed was liver > kidney > adrenal glands > spleen > lung for all treated piglets within one day after dosage. The rank of spleen and lung differed from piglets killed 10 days after supplementation, 21 where lung had a higher retinol concentration than spleen. The higher spleen concentration at one day in the current study is likely due to the scavenging of chylomicra after the large doses given in this study.…”

“…The higher spleen concentration at one day in the current study is likely due to the scavenging of chylomicra after the large doses given in this study. 28 In a prior swine study, 21 spleen acquired more chylomicron-derived 3,4-didehydroretinol in a 4-h timeframe than the lung. The retinol values from the high doses of VA would have had more time to equalize with total body retinol in the Sun et al study considering the 10-day wait period before organ harvest.…”