The pars proventricularis is a region at the entrance of pig stomach, with a keratinized stratified squamous epithelium. In this proximal part of the stomach pathological alterations and ulcers are found often. They impair the fitness of affected animals negatively and possibly can lead to death of the pigs. Due to very few publications little is known about the physiological functions of this epithelium and the pathogenesis of the lesions is still obscure. Therefore, the aim of this study was to characterize the physiological functions of this tissue and to examine whether it is practicable to use an in vitro method to study possible etiological mechanisms. Isolated epithelia of slaughtered pigs were used to determine electrophysiological and transportphysiological parameters with the Ussing- chamber technique. The following results were obtained:
* Healthy and pathologically affected epithelia differ with regard to the electrophysiological parameters. The conductance (GT) of intact tissues amounts to less than 1 mS·cm-2. Consequently this epithelium has to be classified as tight. The short circuit current (ISC) and the GT of the affected tissues are considerably increased. * Healthy as well as damaged epithelia show a positive short circuit current which is mainly based on the transport of sodium. * Both, healthy and affected epithelia show a net absorption of sodium. The sodium transport of damaged epithelia is increased. * The addition of oubain, amiloride and histamine reduces the ISC. * The transport of Cl, mannitol and JNasm through the epithelium occurs on a passive and presumably on a paracellular route. There exists no net transport of chloride. * The increased conductance of damaged epithelium is mainly based on enhanced paracellular conductance. This epithelium becomes more leaky. Consequently, its barrier function is reduced. * A mucosal pH of 2.0 hardly influences the function of normal epithelium, whereas the electro-physiological parameters of affected epithelium are deteriorated immensely.
* When kept in housing conditions with straw pigs have a normal epithelium with a low GT. Housing conditions without straw cause serious lesions of the epithelium within a few days. The results clearly showed that in vitro investigations can contribute to the knowledge about the etiology of pig gastric ulcer. It is easy to distinguish between healthy and damaged epithelia. The studies demonstrated that husbandry conditions without straw may lead to serious damages in the pars proventricularis of pigs. Although the growth rates of pigs are not inevitably reduced the lesions of the epithelium impair the well-being and health of affected animals. Therefore housing conditions of pigs without straw should be discussed as a matter of animal welfare.
