Involvement of the transepithelial calcium transport disruption and the formation of epididymal stones in roosters

Abstract

Epididymal lithiasis is a dysfunction of unknown origin characterized by the formation of calcium stones into the lumen of efferent ductules of roosters. Affected animals present an imbalance in the hormonal responsive systems that regulate the expression of proteins involved in the transepithelial calcium transport, as TRPV6, CaBP-D28K, NCX1, and PMCA. Because the efferent ductules are the major site of fluid and calcium reabsorption in excurrent ducts, it was hypothesized that impairment in local calcium homeostasis would lead to lithiasis. To test this hypothesis, we addressed the expression of these proteins in the epididymal region of affected animals. The present study focused on the investigation of the occurrence, tissue distribution, and physiological impact of the transepithelial calcium transport in roosters under normal and pathological conditions. The results showed that affected roosters presented a significant increase in TRPV6 and CaBP-D28k levels, whereas NCX1 and PMCA were not changed. Such alterations were more conspicuous in the proximal efferent ductules, in which was also observed accumulation of calcium within the epithelial cells. These findings provided the first evidences for the involvement of alteration in the expression of proteins essential for calcium reabsorption as a plausible mechanism for the formation of calcium stones within efferent ductules.

Coupling of TRPV6 and TMEM16A in epithelial principal cells of the rat epididymis

“…However, only TRPV6 is expressed in the male excurrent duct, as demonstrated in this study and others ( Weissgerber et al, 2011 ; Oliveira et al, 2012 ). TRPV5/TRPV6-mediated transcellular Ca 2+ absorption is a multistep process, which begins with passive Ca 2+ entry through apical Ca 2+ channels and is followed by diffusion of Ca 2+ through the cytosol, facilitated by binding to Ca 2+ -binding protein (calbindin-D 28k in the kidney and epididymis and calbindin-D 9K in the intestine) and eventually extrusion of Ca 2+ across the basolateral membranes by the energy-dependent Na + /Ca 2+ exchangers and Ca 2+ -ATPase operating against the Ca 2+ electrochemical gradient ( Hoenderop et al, 2005 ; Oliveira et al, 2012 ). From the point of view of energy input, it is suggested that the initial step of passive entry through TRPV5/TRPV6 channels in the apical membranes is the rate-limiting step.…”

“…TRPV5 is the predominant isoform found in kidney, whereas TRPV6 is found in the intestines, although these tissues coexpressed both isoforms in a region-dependent manner. However, only TRPV6 is expressed in the male excurrent duct, as demonstrated in this study and others (Weissgerber et al, 2011;Oliveira et al, 2012). TRPV5/ TRPV6-mediated transcellular Ca 2+ absorption is a multistep process, which begins with passive Ca 2+ entry through apical Ca 2+ channels and is followed by diffusion of Ca 2+ through the cytosol, facilitated by binding to Ca 2+ -binding protein (calbindin-D 28k in the kidney and epididymis and calbindin-D 9K in the intestine) and eventually extrusion of Ca 2+ across the basolateral membranes by the energy-dependent Na + /Ca 2+ exchangers and Ca 2+ -ATPase operating against the Ca 2+ electrochemical gradient (Hoenderop et al, 2005;Oliveira et al, 2012).…”

Calcium Homeostasis in the Epididymal Microenvironment: Is Extracellular Calcium a Cofactor for Matrix Gla Protein-Dependent Scavenging Regulated by Vitamins

“…However, the restricted localization of the extracellular pH-and Ca 2+ -dependent TRPV6-TMEM16A electrical coupler in the proximal and distal ends of the epididymis as well as in the epididymosomes not associated with extensive Ca 2+ reabsorption could imply the presence of another calcium reabsorption mechanism or that TRPV6 and its coupler TMEM16A have a function other than Ca 2+ reabsorption. Consistent with our speculation, a study of roosters found that those with epididymal stones had raised epididymal expression of TRPV6, although the connection between the two observations is still unclear (Oliveira et al, 2012).…”

Genome‐wide association study reveals novel variants for growth and egg traits in Dongxiang blue‐shelled and White Leghorn chickens

“…; Oliveira et al . ). In chicken, eggshell formation takes place in the uterus and demands plentiful ionic precursors for calcium carbonate (CaCO 3 ).…”