Distribution of Vitamin A, Retinol-Binding Protein, Cellular Retinoic Acid-Binding Protein I, and Retinoid X Receptor β in the Porcine Uterus During Early Gestation1

Abstract

Retinol and retinol-binding protein (RBP), among the major secretory products of the uterine endometrium in the uterine fluid of pigs, are assumed to be of importance for early embryonic development. While uterine RBP has been widely characterized, little information is available on the metabolism of vitamin A itself or other specific binding proteins or nuclear receptors in the uterus of pigs. In the present study, the content and distribution of vitamin A in uterine tissue of pigs during early gestation (Days 14-30) were examined macroscopically and microscopically via autofluorescence and HPLC. In addition, the distribution of specific proteins involved in vitamin A metabolism at the cellular and nuclear level was investigated. Macroscopically, the yellowish-greenish autofluorescence characteristic of vitamin A was observed in uterine endometrium. Microscopy showed that the autofluorescence was associated with glandular and surface epithelium of the endometrium. In these structures, immunoreactive RBP was localized, as was cellular retinoic acid-binding protein I. Retinoid X receptor beta was observed in the nucleus of myometrium and endometrium. The intensity of fluorescence decreased with the progress of gestation. This decrease was paralleled by a decrease in vitamin A content of endometrium and myometrium. In general, vitamin A concentration in the endometrium was higher than in the myometrium (P < 0.01). In the myometrium, if present at all, vitamin A was found almost exclusively as retinyl esters. In the endometrium, the dominant fraction was retinol, representing more than 90% of total vitamin A. These results show for the first time that the yellowish-greenish autofluorescence in the pig uterus can be attributed to vitamin A. Differences in the form of vitamin A present in endometrium and myometrium might point to differences in metabolism. In the myometrium, vitamin A might be stored, and in the endometrium, vitamin A is present primarily as retinol-the form in which it is secreted into the uterine fluid.

Effect of dietary ?-carotene on the accumulation of ?-carotene and vitamin A in plasma and tissues of gilts

“…The vitamin A concentration in uterine tissue corresponds to values for other gilts during early gestation [25]. In this study it has been shown that vitamin A content and distribution in uterine tissue was dependent on the stage of gestation.…”

Within-litter variation in birth weight: impact of nutritional status in the sow

“…Moreover, sows on vitamin A-deficient diets did not experience a reduction in fetal survival and growth at Day 30 of pregnancy , perhaps due to a compensatory increase in the abundance of retinol binding protein (RBP) (Antipatis et al, 2008). Since pig conceptuses secrete RBP prior to onset of elongation and throughout the peri-implantation period, RBP could be an important component of the uterine secretions for early embryonic development (Harney et al, 1990;Schweigert et al, 1999). Thus, elevated levels of RBP in gilts deficient in vitamin A can account for positive outcomes of piglets having low within-litter variation in birth weight.…”

Vitamin A excreted in the urine of canines is associated with a Tamm-Horsfall like protein

“…The autofluorescence of vitamin A under UV excitation at 312 nm was then used to localise the vitamin A-protein complex [26]. To quantify the amount of vitamin A in the native gel, individual lanes were cut into 5 mm-strips.…”