The effects of intestinal ischemia on the levels of serum immunoglobulin A in rats

Many biochemical markers have been investigated in intestinal ischemia. However, the effects of intestinal ischemia on the level of serum immunoglobulin A (IgA) has apparently not been investigated in the literature, although the gastrointestinal system is one of the main sources of serum IgA. The aim of our study was to evaluate the changes of serum IgA levels during intestinal ischemia of varying duration in rats. Group 1 (n=5) was created for control purposes, including the detection of the baseline values and the effects of the anesthetic agents. Group 2 (n=20) rats underwent sham laparotomy. Group 3 (n=20) had 50% of small intestine ischemia by the strangulated obstruction model. Serum samples were obtained by cardiac puncture 1 h after anesthetic agents were given in group 1. On the other hand, serum and intestine samples were obtained at 1 (T1, n=5), 2 (T2, n=5), 4 (T4, n=5) and 6 (T6, n=5) h after the operation in groups 2 and 3. The levels of serum IgA, lactic dehydrogenase (LDH) and alkaline phosphatase (ALP) were determined. Pathologic specimens were graded in a masked manner. IgA levels were abruptly decreased to 8.49±1.58 mg/dl in rats with intestinal ischemia at 1 h after the operation. This decrease in serum IgA at T1 in group 3 was statistically significant compared with the control and sham-operated groups (18.80±1.15 mg/dl, 22.07±1.54 mg/dl, respectively; P<0.01). On the other hand, IgA levels were significantly elevated at T2 in the sham-operated group compared with control and intestinal ischemia groups (26.99±2.96 mg/dl, 18.80±1.15 mg/dl, 14.35±2.62 mg/dl, respectively; P<0.05). The serum IgA levels decreased to above baseline values at T6 in group 2 (19.60±2.78 mg/dl), while they increased to below baseline values in group 3 (17.60±1.28 mg/dl). In group 3, IgA levels were elevated to baseline values, while a significant ischemia occurred at 4 and 6 h after operation. These results suggested that serum IgA is affected earlier by intestinal ischemia and intestinal manipulation. The increase in serum IgA levels may be related to stimulation of the local immune responses in the intestine. On the other hand, abruptly decreasing serum IgA levels in this experimental study may be related to inadequate transport of the synthesized IgA to the systemic circulation, because serum IgA levels were returned to baseline values while a significant ischemia occurred at T4 and T6. According to these results, we conclude that serum and peritoneal fluid IgA levels may be changed by intestinal ischemia and may be used to make an early diagnosis of intestinal ischemia in humans.