RESUMO
The influence of anterior pituitary hormones on the gastrointestinal tract of humans and animals has been reported. Hypophysectomy (HYPOX) in the rat causes atrophy of the intestinal mucosa, reduction of gastric secretion and intestinal absorption, and increased susceptibility to infections. To our knowledge, there are no studies on the humoral immune response of the gut-associated lymphoid tissue after HYPOX. We have reported that decreased secretion of vasopressin and oxytocin due to neurointermediate pituitary lobectomy (NIL) diminishes humoral and cell-mediated immune responses. However, no data have been published on whether NIL can affect intestinal immune responses. We analyzed the effects of HYPOX and NIL on bacterial colonization of the intestinal lumen, Peyer's patches, and spleen as well as the serum immunoglobulin G (IgG) and IgM and specific intestinal IgA levels in response to Salmonella enterica serovar Typhimurium oral infection. Results showed the following: (i) Salmonella serovar Typhimurium was eliminated from the intestinal lumen at the same rate in rats that underwent a sham operation, HYPOX, and NIL; (ii) Salmonella serovar Typhimurium colonization of Peyer's patches and spleen was significantly higher in both HYPOX and NIL rats than in sham-operated rats; (iii) serum IgG and IgM and intestinal IgA against surface proteins of Salmonella serovar Typhimurium were significantly lower in HYPOX and NIL rats than in sham-operated rats; and (iv) compared to NIL rats, higher Peyer's patch and spleen bacterial colonization and decreased IgG, IgM, and IgA production were observed in HYPOX rats. We conclude that hormones from each pituitary lobe affect the systemic and gastrointestinal humoral immune responses through different mechanisms.
Assuntos
Imunoglobulina A/sangue , Imunoglobulina G/sangue , Imunoglobulina M/sangue , Neuro-Hipófise/cirurgia , Salmonelose Animal/sangue , Salmonella typhimurium , Animais , Hipofisectomia/efeitos adversos , Ratos , Salmonelose Animal/imunologiaRESUMO
OBJECTIVE: Chronic stress is characterized by an increased activity of the hypothalamic-pituitary-adrenocortical axis and decreased humoral and cell-mediated immune responses. In the rat, corticosterone is the principal natural immune suppressor. Neurointermediate pituitary lobectomy (NIL) in rats induces diabetes insipidus and protracted increases in basal adrenocorticotropin and corticosterone plasma levels, a situation that resembles chronic stress. In this paper, we evaluated the effects of NIL on humoral (hemagglutinin titers and footpad swelling to sheep red blood cells--SRBC) and cell-mediated immune responses (contact hypersensitivity to dinitrochlorobenzene). METHODS: The studies were conducted on NIL Wistar rats (body weight 150-200 g) 3 weeks after surgery. For comparisons, nonoperated control rats were used. RESULTS: NIL resulted in an increased water intake. Body weight gain and adrenal, thymus, and spleen weights were within the range of nonoperated controls. Eight days after SRBC immunizations a second SRBC injection into the footpad resulted in a decreased swelling response in NIL rats. The hemagglutinin titers were also reduced in the NIL rats. CONCLUSIONS: These results indicate that: (1) NIL reduces humoral immune responses and decreases the cell-mediated immune response; (2) the immune alterations are most likely due to the increased activity of the hypothalamic-pituitary-adrenocortical axis induced by NIL, and (3) NIL animals constitute a valuable paradigm to study hypothalamic-pituitary-immune interactions.