Origin of the Low pH Values along the Proximal Duodenum in Sheep

Abstract

Sheep were fitted with cannulas beyond the pylorus and proximal to the common biliarypancreatic duct in order to measure the amount of acidic contents flowing from the abomasum and the pH values in relation to antroduodenal contractile activity. In both the antrum and proximal duodenum, the mean pH values averaged 2.6 during 90 % of the recording time. They rose by 1.5 units in the proximal duodenum during the short periods of antroduodenal quiescence, at which time the gastric outflow of acidic chyme was reduced from 200ml/h to almost zero. Such variations persisted after biliary by-pass to the jejunum.An increase in duodenal pH was progressively developed in an isolated duodenal loop proximal to the bile duct when the gastric outflow was reduced, whereas no changes occurred when the loop was perfused continuously with saline at pH 3 at the rate of 200 ml/h.The results indicate that the continuous delivery of acidic gastric contents in sheep is responsible for the low duodenal p H values for a distance of 2 b 3 0 c m beyond the pylorus. Conversely, the transient increase in duodenal pH during lower gastric outflow was associated with the disruption of the normal equilibrium between duodenal alkaline secretion and the acid load imposed by the stomach.

Loss of Forestomach Motility in Sheep Experiencing Ruminal Lactic Acidosis is not Dependent on Duodenal Acidification by Lactic Acid

“…Lactic acid solutions which have caused inhibition of forestomach motility (2, 6-9, 15) or induced premature duodenal RSAs when infused into the proximal duodenum (6,8) possessed p H values of 2.0 o r less. Since this level of acidity greatly surpassed that which normally exists in the ovine abomasum and duodenum (12), the loss of forestomach motility which accompany duodenal acidification by these acidic solutions may represent an artificial situation.…”

“…From these findings it is concluded that the loss of forestomach motility which occurred in sheep experiencing ruminal lactic acidosis did not result from acidification of the proximal duodenum by lactic acid produced in the forestomach. Since the p H of duodenal contents is directly dependent on the p H of the continuous incoming acidic abomasal contents (12,13), it would appear that lactic acid delivered to the abomasum from the forestomach, in ruminal lactic acidosis, is incapable of further decreasing the normally low pH of abomasal contents.…”

Évacuation de la caillette chez les ruminants adultes

“…La sensibilité du débitmètre a été accrue par l'utilisation d'amplificateurs dédiés (Leveille et al, 1979;Poncet et al, 1977). L'instabilité de la ligne de base a été corrigée, soit par un rattrapage analogique du 0 (Leveille et al, 1979), soit grâce à un traitement informatique en temps réel du signal et à une reconnaissance automatique des débits unitaires (Malbert et al, 1987;Malbert et Ruckebusch, 1987a). A présent, cette méthode est susceptible de fournir sur plusieurs jours le débit instantané et le volume total de chyme ayant transité au travers du pylore.…”

“…L'exclusion des sécrétions pancréato-biliaires au moyen d'une canule située dans le canal cholédoque commun au niveau de la flexure hépatique conduit à une élévation du pH du contenu duodénal de 0,3 unité. Cependant, malgré l'impossibilité matérielle d'un reflux alcalin, les périodes de repos repérées au niveau du duodénum sont associées à une élévation du pH de 4 unités; un effet à tous égards identique à celui observé sur les animaux témoins (Malbert et Ruckebusch, 1987a).…”