Feeding induces lipid accumulation and increased Na⁺ transport in in vitro Necturus antrum

We investigated the effects of feeding on lipid accumulation and transepithelial transport using in vitro Necturus gastric antral mucosae. Antra from fed Necturi were examined for lipid accumulation using light, fluorescence, histochemical, and electron microscopy. Ussing chambers were used for measurement of potential difference (PD), transepithelial resistance (R(t)), short-circuit current (I(sc)), and unidirectional fluxes of ²²Na⁺ and [³H]mannitol. Light microscopy of antra from 2-day postfed animals showed many intracellular lipid granules in surface mucous epithelial cells. These granules could be distinguished from other intracellular organelles by their high affinity for osmium and the lipid fluorescent probe Nile red. Glycoprotein cytochemical staining showed these granules to be distinct from the epithelial cell mucous granules. Electron microscopy showed the lipid granules to be part of a membranous reticular network. Two-day postfed animals also had a ~3.5-fold increase in amiloride-sensitive I(sc) and PD, a decrease in R(t), and an increased luminal-to-serosal Na⁺ fluxes. Transepithelial [³H]mannitol fluxes were low and remained unchanged n both fasted and 2-day postfed animals. After 2 days of feeding, the PD and I(sc) began to decrease followed by a secondary increase in R(t). Feeding Necturi a corn oil diet did not induce the appearance of either cellular lipid or alterations in I(sc) but produced a transient increase in R(t). Our data show that feeding (goldfish) to Necturi causes an increase in both lipid accumulation and amiloride-sensitive Na⁺ transport in gastric antral cells.