Objective: The role of arginine vasopressin (AVP) as a direct immune regulator has not yet been clarified, and more work is needed to assess its involvement in the immunoneuroendocrine network. In the present study, the effects of neurointermediate pituitary lobectomy (NIL) and desmopressin (DP), an agonist of AVP, on acute experimental autoimmune encephalomyelitis (EAE) in female Lewis rats were evaluated. The activity of the hypothalamic-pituitary-adrenocortical (HPA) axis was also assessed. Methods: Five groups of rats were used, as follows: (1) sham-operated (SHAM) rats, (2) SHAM + DP rats, (3) NIL rats, (4) NIL + DP rats and (5) untreated normal control rats. DP treatment started 2 weeks after surgery, and immunization to induce EAE was carried out 1 week later. Results: SHAM rats developed full-blown clinical and histological signs of EAE and activation of the HPA axis. SHAM + DP animals had mild clinical signs of EAE, inflammatory infiltrations in the spinal cord and an activated HPA axis. NIL animals developed minimal EAE, scanty spinal cord inflammation and no changes in HPA axis activity. NIL + DP rats developed severe clinical signs of EAE, extensive spinal cord inflammatory infiltrations and marked activation of the HPA axis. Conclusions: NIL decreased the cell-mediated immune response, while DP in NIL animals restored the immune response. AVP is directly involved in the maintenance of immune competence.
The role of AVP controlling the mean arterial blood pressure (MBP) in basal conditions remains unclear. We described that neurointermediate pituitary lobectomy (NIL) in rats, induced an early but transient diabetes insipidus and low MBP (8 weeks after lobectomy). To elucidate the chronological effects of NIL, we evaluated the AVP serum levels, water intake and urine output (diabetes insipidus, DI), and MBP immediately (0 to 6 hours post NIL) and 3, 15, 45 and 90 days post NIL. The renin, angiotensin II and aldosterone system (RAAS) was assessed at 3 and 45 days post NIL. Values were compared with the respective SHAM operated groups. Results: NIL caused significant and permanent AVP serum level decrease (10.6 ± 0.8 vs 2.4 ± 0.16 pg/ml (SD), SHAM vs NIL), transient DI (15‐30 days of duration) and permanent decrease of the MBP in 70% of the NIL animals (106.8 ± 3.15 vs 73.8 ± 3.2 mmHg). Hypotension was apparent 20‐30 minutes after NIL. No significant differences in the RAAS were evident.ConclusionsWe propose that in non‐stressed animals, basal serum levels of AVP are required to maintain the hydro‐electrolytic balance and MBP. Further studies are needed to explain why some animals did not develop hypotension, and to determine how cardiovascular, renal and hormone adaptive mechanisms in the NIL group support their survival.Supported by UAA‐PIFF and CONACYT, México and the Jarislowsky and L. Carr‐Harris Foundations
Immune and vascular endothelial cells possess arginine vasopressin (AVP) receptors. AVP is an important stimulating/regulatory hormone in acquired immunity, whereas its role on innate immunity (INIM) is not well known. Neurointermediate pituitary lobectomy (NIL) in the rat causes permanent low AVP serum levels. Here, we investigate the AVP and INIM relationship in NIL rats (3 weeks after surgeries) subject to INIM tests: Phagocytic index (PI) (peritoneal macrophages (Mθ) erytrophagocytosis), and Skin Evans blue extravasation‐histamine doses‐response test. In the Study 1, NIL group was compared against Intact control (IC), sham operated (SHAM) and anterior pituitary lobectomysed (AL) groups. In the study 2, NIL group was compared against IC, NIL+desmopressin (a synthetic analog of AVP) and IC+conivaptan (antagonist of V1a‐V2 AVP receptors) groups. Results: Study 1 showed that as compared with the IC and AL groups, PI was significant decreased in NIL animals. In the Evans blue extravasation‐histamine test study, a significant and similar increases of skin edema histamine doses‐dependent occurred in NIL and IC+conivaptan groups, whereas no significant differences in IC and NIL+desmopressin groups were appreciated.ConclusionAVP plays an important role in phagocytic activity of the peritoneal Mθ and for the stabilization of the vascular endothelial cells permeability during histamine inflammation.Supported by UAA‐PIFF 14‐1. Universidad Autónoma de Aguascalientes, México and the Jarislowsky and Lloyd Carr‐Harris Foundations.
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