The localization of somatostatin-like immunoreactivity in the alimentary tract of the sheep with observations on the effect of an infection with the parasite Haemonchus contortus.

ABSTRACT

Cells containing somatostatin immunoreactivity were localized in the alimentary tract of parasite-free sheep by indirect immunocytochemistry, using an antiserum raised to ovine somatostatin. Nerve fibres showing somatostatin-like immunoreactivity were identified in the oesophagus, reticulum wall and groove, rumen pillar and wall, omasum sulcus and abomasum. Varicose fibres were found in the myenteric plexuses of the duodenum, jejunum, ileum and colon. The greatest distribution of endocrine cells (99 cells mm-2) was found in the antrum of the abomasum with 47, 29, 12 and 6 cells mm-2 respectively in the fundus, the first part of the duodenum, mid-jejunum and ileum. Some of the parasite-free sheep which had never experienced infection with larvae of the abomasal nematode, Haemonchus contortus, were paired with similar sheep in an experiment to investigate the effect of parasitism on nitrogen metabolism in the small intestine. The protocol of this experiment required observations before and after parasite infection, with final observations 2 weeks after removal of the infection by treatment with an anthelmintic drug. The sheep were then killed and tissues taken from each paired animal. Tissues from the recently parasitized sheep showed increases of D cells in the fundus and antrum of the abomasum. At present it is not clear if these increases were related to parasitism, per se, or were the post-treatment indicators of healing and recovery from infection with parasite larvae.