Restraint effects on stress-related hormones and blood natural killer cell cytotoxicity in pigs with a mutated ryanodine receptor.

A mutation in the ryanodine receptor gene (RYR1) of the calcium release channel is responsible for increased stress susceptibility in pigs. In the present study, the relation of a mutation in RYR1 with the neuroendocrine (stress-related hormone) response and the immune defense represented by natural killer cell cytotoxicity (NKCC) during a 4-h restraint and recovery phase in 60 male pigs was investigated. Blood samples were collected from pigs previously divided into RYR1 genotypes (nn, Nn, NN), based on PCR amplification and restriction analyses. The blood samples collected during the restraint and recovery phases of the experiment were used to determine NKCC ((51)Cr-release assay), large granular lymphocyte number (hematologic method), and plasma concentrations of prolactin (PRL), GH, ACTH, and cortisol (COR) (by specific RIA). The greatest degree of NKCC response (P < 0.05) to restraint stress relative to controls was observed for the stress-susceptible homozygote group (nn). Measures of stress-related hormones were positively correlated with NKCC during the entire experimental period (P < 0.001 for all investigated hormones) in the nn group. Immunostimulatory effects in the early (0-60 min) phase of restraint were associated with increased hormone responses, especially PRL and GH. In the late (180-240 min) phase of stress and the recovery phase (480 min), a decrease in immune response was accompanied by an elevated COR response in all RYR1 genotypes. Moreover, divergent responses of both PRL (greatest in nn, P < 0.001) and GH (greatest in NN, P < 0.001) to the 4-h restraint were observed. Our results suggest that stress-susceptible RYR1-mutated homozygotes develop a greater level of immune defense, including cytotoxic activity of NK cells, and accompanied by more pronounced stress-induced changes in neuroendocrine response than stress-resistant heterozygous (Nn) and homozygous (NN) pigs.

Blood and spleen natural killer cell cytotoxicity after exposure to open field stress in rats: the effect of spontaneous locomotor activity.

In the present study we compared the effects of acute (30 min), white and illuminated open field (OF) stress on behavioral, immune and endocrine variables between rats divided into high (HR) and low (LR) responsive to novelty and in a non-divided group. It was found that OF-induced behavioral depression which was in parallel to suppression of both blood and spleen natural killer cell cytotoxicity (NKCC), large granular lymphocyte (LGL) and lymphocyte numbers occurred in stressed LR rats only. There was no significant difference in the plasma level of corticosterone (COR) and testosterone (TST) between HR and LR rats. In contrast, when the HR and LR groups were examined together (the non-divided group), no significant influence of OF stress on behavioral activity or NKCC was observed. These results emphasize that individual differences as measured by spontaneous locomotor activity play the important role for the study of the mechanisms involved in stress-induced immunomodulation and indicate that OF stress-induced behavioral depression in low reactivity animals may be accompanied by impaired defence against viral infections and neoplastic growth, which is functionally related to NKCC.

Stress-induced changes in peripheral natural killer cell cytotoxicity in pigs may not depend on plasma cortisol.

The study examined cortisol (COR) involvement in stress-related changes in natural killer cell cytotoxicity (NKCC). The relationship between blood COR level, phasic changes in NKCC, and the number of large granular lymphocytes (LGL) was examined in pigs during the course of 4-h immobilization stress (IMB) and for 6 days after its termination. NKCC was determined using 18-h 51Cr-release assay, LGL number was assessed with a standard hematological method, and plasma COR level was measured by radioimmunoassay. The blood level of COR was increasing during IMB (max 446Delta% at the second hour) and decreased after its termination (max -59Delta% on day 2). Changes in NKCC level and LGL number were biphasic; i.e., an initial increase in both measures (NKCC max 24Delta%, LGL max 18Delta%) in an early phase of stress (0-1h) was followed by their subsequent decrease (NKCC max -35Delta%, LGL max -41Delta%) in the late phase (3-4 h) of stress, which persisted for several days after termination of IMB. Thus, in the early phase of stress, there was a positive correlation between NKCC, LGL number, and COR levels (all elevated); a positive correlation between the measures also occurred after termination of IMB (all decreased). A negative correlation between COR and NKCC, which might be indicative of COR-related immunosuppression, was found only in the late (3-4 h) phase of stress. It is concluded that COR may be only one of multiple factors (possibly antagonistic) determining an actual immune response during stress.

Electrolytic lesions of the lateral hypothalamus influence peripheral blood NK cytotoxicity in rats.

Bilateral electrolytic lesions of the lateral hypothalamic (LH) area in Wistar rats result in a time-dependent blood NK cytotoxicity changes as measured by the 51Cr-release (for entire cell population) and agarose (for a single-cell) assays. NK activity against YAC-1 and K-562 cells shifts from depression through enhancement to another depression on the 2nd, 5th and 21st post-lesion day, respectively, as compared to both LH sham-operated animals and the pre-lesion baselines. This effect is not attributable to malnutrition and dehydration resulting from ingestive impairments evoked by LH lesions. No significant change in NK cytotoxicity was found after destruction of the medial hypothalamus (MH). The results indicate that LH, under normal conditions, which may be considered as a dynamogenic and stressogenic hypothalamic area is essential for proper regulations of NK cytotoxicity at both population and single-cell level.

The influence of immobilization stress on natural killer cytotoxic activity in halothane susceptible and resistant pigs.

In halothane-susceptible (Hal+) and halothane-resistant (Hal-) Belgian Landrace pigs, the influence of immobilization stress on cytotoxic activity of natural killer (NK) cells was evaluated. Four hour immobilization causes biphasic changes in cytotoxicity, i.e. an initial increase followed by a subsequent depression. In both groups of pigs stress-induced suppression of NK cell activity lasted for several days in the post stress period. Throughout the experiment, i.e. before, during and after stress, the level of cytotoxicity was higher in Hal+ than in Hal- pigs.