Vitamin D3 Receptor Immunohistochemistry in Sheep and Goat Intestine

Abstract

Disturbed calcium homeostasis during the peripartal period is a major problem in domesticated ruminants. Clinical signs of hypocalcaemia shortly after calving (periparturient paresis) occur in cattle, predominately in elder animals. On the contrary, in sheep and goat, periparturient paresis is mainly evident several weeks before and only in some cases after parturition. In high‐yielding dairy goats, however, periparturient paresis also occurs – as in the dairy cow – during the peripartal period (Ruffin et al., 2002). Vitamin D3 receptors (VDR) participate in the regulation of calcium homeostasis by increasing the efflux of calcium from bone and dietary sources into blood. The nutritional availability of calcium during the peripartal period has been examined in cattle: VDR concentrations in colon decrease with age, being significantly higher during pregnancy and lactation and are temporarily lower at parturition (Goff et al., 1991). However, similar data have not been evaluated for sheep and goat. Thus, tissue specimens of small and large intestines were collected from lambs and non‐lactating, non‐pregnant adult animals of both species. Formaldehyde fixed and microwave treated paraffin sections were used for VDR immunohistochemistry employing a biotinylated monoclonal rat antibody and streptavidin peroxidase technique. Preliminary results in adult sheep showed that VDR immunoreactivities generally were higher in deep parts of crypts, decreased towards openings and were low in surface epithelium. Staining was most prominent in duodenal mucosa, lower in jejunum and further decreased in ileum and colon. It was lowest in caecum. Smaller numbers of immunopositive cells and reduced staining intensities resulted in weaker immunoreactions in the latter segments of small and large intestines. In addition to nuclear tinction, cytoplasmic staining was mainly evident in duodenum, at lower levels in jejunum and negligible in ileum, colon and caecum. Immunohistochemistry of goat and lamb intestines are currently performed, thus the effects of age and species are presently unknown. Our preliminary results indicate that VDRs are highly expressed at the site of presumed maximal intestinal calcium resorption.References Ruffin, DC et al. 2002, In: Sheep and Goat Medicine, DG Pugh (ed), Philadelphia: WB Saunders.Goff, JP et al. 1991. J. Dairy Sci. 74, 4022–4032.