Morphologic characterization of castor oil-induced colitis in ponies.

The study investigates the effects of castor oil on ten ponies which led to severe diarrhea, with analysis of the morphological changes that occur in the intestines of the ponies.

Overview of the Study

• The researchers conducted their study on ten ponies that ranged from 17 months to 20 years in age and weigh between 160 to 250 kg. Every pony was administered oral doses of castor oil, which induced severe diarrhea within 24 hours.
• The symptom of diarrhea became critical between 24 and 48 hours following the administration of castor oil and started to decrease around 72 hours after dosing.
• To examine the impact of castor oil administration, some ponies were euthanized at several points (24, 48, and 72 hours) after dosing. The intestinal tissue from these ponies was then closely inspected both histologically and ultrastructurally to identify the changes.

Symptoms and Morphological Changes

• Within 24 hours of consuming castor oil, significant morphological changes were observed in the lining of cecum and ventral colon. The changes included substantial superficial epithelial erosion and the infiltration of neutrophils. There were also pathological changes in the ileum, with villous tips’ epithelium separating from the lamina propria.
• Microscopic examination of the cecal mucosa showed exposed basement membranes in most regions, barring the necks of crypts. Superficial enterocytes in the cecum and ventral colon underwent changes including the loss of microvilli, distortion of the terminal web within the cytoplasm, enlargement of the cytoplasmic matrix leading to the formation of precipitates and the widening of the spaces between junctional complexes.

Results at 48 hours and Healing process

• The erosion in the cecum and ventral colon was less extensive in ponies examined 48 hours after treatment compared to those examined at 24 hours. Most of the basement membranes adjacent to crypts were covered with cuboidal enterocytes.
• These cells underwent ultrastructural changes that were characterized by irregular microvilli on the cytoplasmic extensions and multiple free ribosomes. The changes showed that immature enterocytes had migrated from the crypts to the eroded mucosal surface, indicating a healing process had begun.