Expression patterns of intestinal calcium transport factors and ex-vivo absorption of calcium in horses

BACKGROUND: In many species, the small intestine is the major site of calcium (Ca(2+)) absorption. The horse differs considerably from most other species with regard to the physiology of its Ca(2+) metabolism and digestion. Thus, this study was performed to get more information about the transcellular Ca(2+) absorption in the horse.Two mechanisms of intestinal Ca(2+) absorption are described: the passive paracellular pathway and the active, vitamin D-dependent transcellular pathway. The latter involves the following elements: vitamin D receptors (VDR), transient receptor potential vanilloid channel members 5 and 6 (TRPV5/6), calbindin-D9k (CB), the Na/Ca exchanger (NCX1) and the plasma membrane Ca-ATPase (PMCA). The aim of the present study was to investigate the protein and mRNA expression patterns of VDR, CB and TRPV6 and the ex-vivo Ca(2+) absorption in horses, assessed by qualitative and quantitative RT-PCR, western blot, immunohistochemistry and the Ussing chamber technique. RESULTS: Highest CB and TRPV6 mRNA levels were detected in the duodenum as compared to the middle parts of the jejunum and ileum and several sites of the large intestine. VDR mRNA levels did not change significantly throughout the intestine. TRPV5 mRNA was not detectable in the horse intestine. The highest VDR and CB protein levels were measured in the duodenum. Ussing chamber studies revealed ex-vivo Ca(2+) absorption only in the duodenum, but not in cecum and specific sites of the colon. CONCLUSION: The present findings suggest that TRPV6, CB and VDR may be involved in active intestinal Ca(2+) absorption in horses, as described for other mammals. TRPV5 may not play a major role in this process. Furthermore, the expression patterns of these Ca(2+) transport elements and the results of the Ussing chamber procedure indicate that a significant part of active intestinal Ca(2+) absorption occurs in the duodenum in this species

TRPV6 and Calbindin-D9k-expression and localisation in the bovine uterus and placenta during pregnancy

Transient receptor potential channel type 6 (TRPV6) and Calbindin-D9k (CaBP-9k) are involved in the active calcium (Ca2+) transport mechanism in many tissues including placenta and uterus, suggesting a role in the establishment and maintenance of pregnancy. Moreover, TRPV6 and CaBP-9k seem to support the materno-fetal Ca2+ transport that is crucial for fetal Ca2+ homeostasis, bone growth and development. However, it is unknown if these proteins are also involved in the aetiology of pathologies associated with parturition in cows, such as retained fetal membranes (RFM). The aim of the current study was to create an expression profile of uterine and placentomal TRPV6 and CaBP-9k mRNAs and proteins during pregnancy and postpartum in cows that discharged the fetal membranes in comparison to cows that retained them. The results of the present study demonstrate a dynamic expression of TRPV6 and CaBP-9k during pregnancy in the bovine uterine endometrium and placentomes, suggesting a functional role for these proteins in Ca2+ metabolism during pregnancy. The temporal and spatial expression patterns indicate that TRPV6 and CaBP-9k may be involved in materno-fetal Ca2+ transport, mainly through an interplacentomal transport, and that both proteins may participate in physiological processes that are crucial for fetal and placental development. However, neither TRPV6 nor CaBP-9k seem to be causative in the retention of fetal membranes. Transient receptor potential channel type 6 (TRPV6) und Calbindin-D9k (CaBP-9k) sind wichtige Elemente des aktiven Calcium (Ca2+) Transport in vielen Geweben und scheinen an der Etablierung und Aufrechterhaltung der Trächtigkeit beteiligt zu sein. Im Uterus sind TRPV6 und CaBP-9k als wichtige Faktoren für die myometriale Kontraktilität und Sekretion von Matrixkomponenten beschrieben. In der Plazenta scheinen beide Proteine am materno-fetalen Ca2+ Transport beteiligt zu sein. Ob TRPV6 und CaBP-9k ein Rolle in der Entstehung von Geburtspathologien spielen ist unbekannt. Das Ziel dieser Studie ist ein Expressionsprofil von uterinem und plazentärem TRPV6 und CaBP-9k Protein und mRNA während der Trächtigkeit des Rindes zu erstellen sowie die plazentäre Expression von Tieren mit Nachgeburtsverhaltung (NGV) der von Tieren mit physiologischer Nachgeburtsablösung gegenüberzustellen. Die Ergebnisse dieser Studie demonstrieren eine zeitlich dynamische Expression von TRPV6 und CaBP-9k in Uterus, Plazenta und fetalen Membranen und lassen einen Einfluss beider Proteine auf den Verlauf und Erhalt der Trächtigkeit des Rindes vermuten. Die Lokalisation sowie das zeitliche Expressionsmuster deuten auf eine Rolle beider Proteine am interplazentären materno-fetalen Ca2+-Transport hin. Zudem scheinen beide Proteine einen Einfluss auf die fetale und plazentäre Entwicklung zu haben. Dennoch scheinen weder TRPV6 noch CaBP-9k eine Rolle bei der Entstehung von NGV zu spielen

Uterine and placental expression of HPGD in cows during pregnancy and release of fetal membranes

15-Hydroxyprostaglandin dehydrogenase (HPGD) plays a key role in prostaglandins (PGs) catabolism. Its expression and activity appear to be regulated by progesterone (P4). We investigated the HPGD mRNA-expression and protein localization in placentomes and interplacental uterine sites throughout gestation (Study I), and after fetal membranes retention (RFM) compared with normally delivered fetal membranes (DFM) (Study II). Furthermore, we analyzed the influence of aglepristone (AP), dexamethasone (GC) or cloprostenol (CP), on HPGD expression in bovine placentomes (Study III). Tissues from late gestation (D272) and at normal term (NT) served as controls. HPGD was highest in all sites at the beginning of pregnancy and at (NT). Following induced parturition HPGD was lower after (AP) and (GC) compared with (NT), and was similar in RFM and DFM. Placentomes stained primarily in fetal compartments; interplacentomal signals were observed in endometrial glandular and luminal epithelium. Results indicate that HPGD may play a role during establishment and termination of gestation