Expression of retinol‐binding protein and cellular retinol‐binding protein in the bovine ovary

Abstract

Retinol (vitamin A) is essential for reproduction, and retinoids have been suggested to play a role in ovarian steroidogenesis, oocyte maturation, and early embryonic development. Retinol is transported systemically and intercellularly by retinol-binding protein (RBP). Within the cell, cellular retinol-binding protein (CRBP) functions in retinol accumulation and metabolism. Since the actions of retinoids are mediated, in part, by retinoid-binding proteins, the objective of this study was to investigate cell-specific expression of RBP and CRBP in the bovine ovary. Immunocytochemical analysis (ICC) localized RBP to the thecal and granulosa cell layers of antral and preantral follicles with the most intense staining in the cells of large, healthy follicles. The tunica adventitia of arterial blood vessels also exhibited RBP staining. Immunostaining of CRBP was most intense in the granulosa cells of preantral follicles and present, but diminished, in thecal and granulosa cells of antral follicles. Within the corpus luteum, both proteins were observed in large luteal cells, but only RBP was observed in small luteal cells. Northern blot analysis demonstrated that thecal and granulosa cells from antral follicles and luteal tissue expressed RBP and CRBP mRNA. Synthesis and secretion of RBP by thecal cells, granulosa cells, and luteal cells were demonstrated by immune-complex precipitation of radiolabeled RBP from the medium of cultured cells or explants, followed by SDS-PAGE and fluorography. Follicular fluid was collected from small (<5 mm) and large (8-14 mm) follicles, pooled according to follicular size, and analyzed for retinol, RBP, estradiol-17beta, and progesterone. Concentrations of retinol, RBP, and estradiol were greater in the fluid of large follicles. Results demonstrate retinoid-binding protein expression by bovine ovaries and provide physical evidence that supports the concept that retinoids play a role in ovarian function.

Oocytes recovered from cows treated with retinol become unviable as blastocysts produced in vitro

“…the follicle). Serum-derived follicular ROH can bind to specific protein in granulosa cells (Brown et al 2003) and the oocyte (Mohan et al 2001). After entry into the cell, ROH can be metabolized to RA, which can then be bound by specific CRABPs.…”

“…While retinol-binding protein (RBP) is required for the intercellular transport of ROH, cellular retinol-binding protein (CRBP) is responsible for transporting intracellular ROH that may be either stored or metabolized to retinoic acid (RA), the most important retinoid metabolite required for vertebrate embryogenesis (Morris-Kay & Ward 1999). Bovine granulosa cells synthesize RBP and CRBP (Brown et al 2003), and RBP mRNA has been detected in the oocyte (Mohan et al 2001). Regulation of intracellular RA concentrations is to a great extent controlled by cellular RA-binding proteins (CRABPs).…”

Effect of all-trans retinol on in vitro development of preimplantation buffalo embryos

“…Retinol treatment in combination with super ovulation improves the developmental competence of resultant embryos (Eberhardt et al, 1999). Earlier studies have reported the presence of retinol in follicular fluid (Schweigert and Zucker, 1988;Brown et al, 2003), stating that vitamin-A concentrations to be highest in large nonatretic follicles and lowest in small atretic follicles correlated with estradiol concentrations. Retinol improves embryonic development of bovine oocytes in vitro, indicated by increased blastocyst rate (Livingston et al, 2004).…”

The Roles of Vitamin A for Cytoplasmic Maturation of Bovine Oocytes

“…Dev. 51: [23][24][25][26][27][28][29][30][31][32][33][34][35] 2005) itamin A is one of the fat-soluble vitamins and is well known to regulate development, cellular growth and differentiation, and tissue function [1,2]. Since the earliest research into vitamin A function in cattle reproduction [3,4], vitamin A and its metabolites (Fig.…”

“…In fact, both BC and ROL exist in bovine follicular fluid [5,31,32] in proportion to their blood concentrations [31,32]. In addition to their passive free access to follicular fluid, there are also the selective mechanisms of BC and ROL incorporation into follicles with their respective carrier molecules, and this might partly explain their different concentrations in follicular fluid and plasma [5,33]. BC cleavage activity exists in bovine granulosa cells [34], which implies the local (intrafollicular) conversion of BC to ROL.…”