Meeting Abstract

P2.145  Sunday, Jan. 5 15:30  Developmental calcium uptake and chorioallantoic membrane expression of calbindin-D_28K by viviparous Zootoca vivipara embryos under manipulated ex utero calcium provision. WIESSNER, G*; STEWART, J R; HEULIN, B; ECAY, T W; East Tennessee State University, Johnson City; East Tennessee State University, Johnson City; Station Biologique de Paimpont, France; East Tennessee State University, Johnson City gwiessne@gustavus.edu

Zootoca vivipara is a reproductively bimodal lizard with geographically distinct oviparous and viviparous populations. Viviparous neonates contain only 75% of the calcium of oviparous hatchlings. A possible explanation for this difference is greater efficiency of shell calcium uptake by oviparous embryos compared to placental calcium uptake by viviparous embryos. To test the hypothesis that viviparous embryos are responsive to variation in calcium availability, we developed an ex utero culture system for viviparous Z. vivipara embryos and assayed embryonic calcium uptake and chorioallantoic membrane expression of calcium transport proteins. Embryos cultured at stage 37, prior to significant placental calcium uptake survive to stage 40 just prior to hatching but calcium accumulation is significantly greater for embryos cultured in 2 mM calcium media than in nominally calcium free media suggesting that embryonic calcium transport is maintained in culture. Assay of media calcium reveals that calcium uptake occurs at stage 40. Chorioallantoic membrane expression of calbindin-D_28K, a marker for calcium transport activity, is significantly greater at stage 40 for embryos cultured in 2 mM calcium than in the absence of calcium. Furthermore, calbindin-D_28K expression is maintained in media supplemented with calcium, but declines in the absence of available calcium. These results demonstrate that: 1) ex utero culture is a new experimental system to study viviparous Z. vivipara embryonic calcium metabolism, 2) chorioallantoic membrane calbindin-D_28K expression is sensitive to culture media calcium, and 3) embryonic calcium uptake is a very late event in Z. vivipara development.