Characteristics of innate (nonspecific) and acquired T cell immunity, resting metabolic rate, hor monal and reproductive status, morphological traits of maturation and aggressive behavior were studied in two sample groups of Campbell's dwarf hamster males (Phodopus campbelli Thomas, 1905) selected in three generations for high and low humoral immune response to sheep red blood cells (SRBC). The groups of males with low and high immune responses (LIR and HIR, respectively) to SRBC did not differ statistically in the intensity of delayed type hypersensitivity cutaneous response to phytohemagglutinin (T cell immunity test), the activity of the peroxidase-endogenous hydrogen peroxide system of neutrophils (characteristic of the innate immunity state), the white blood cell counts, the resting metabolic rate, body weight, anogenital distance at the age two months, testosterone level in the blood before immunization and at the peak of sec ondary immune response to SRBC, or the blood cortisol level in response to social conflict (encountering). LIR males had a significantly higher background blood cortisol level and were less aggressive (reaction to the stranger male). The midventral sebaceous gland was less developed in them at the age of two months. We observed no differences in the time of first litter birth after uniting LIR and HIR males in pairs with intact females; however, females in pairs with LIR males had smaller numbers of pups in the litter. The results of comparison do not favor the immunocompetence handicap hypothesis, which assumes the existence of a trade off between the immunocompetence and reproductive effort.
We tested two hypotheses. 1) SkQ1 positively affects postnatal development of hamsters in litters born to parents receiving long-term SkQ1 treatment. 2) SkQ1 accelerates maturation of juvenile females receiving the antioxidant treatment from 10 days of age. Parental pairs were kept in an outdoor vivarium under conditions close to natural. At the age of 25 days, juvenile males in litters born to parents treated daily with SkQ1 (50 nmol/kg per os) had higher epididymis mass. Both the size of a litter and SkQ1 affected epididymis mass in young males. Both the litter size and SkQ1 affected uterus mass in 25-day-old females. Juvenile females who received SkQ1 treatment from 10 days of age demonstrated earlier opening of the vagina. This experiment was replicated with the same result. At the age of 2.5 months, virgin females treated with SkQ1 from the early age demonstrated higher ovary mass.
We studied demographic effects of the mitochondria-targeted antioxidant SkQ1 on free-breeding Campbell dwarf hamsters (Phodopus campbelli, Thomas, 1905, Rodentia, Cricetidae) in an outdoor vivarium with seasonally varying day length and temperatures. The animals were kept in pairs from their young age. We removed litters from parental cages at their age of 25 days. Experimental hamsters received daily 50 nmol/kg SkQ1 with water by oral dosing, whereas control animals received water. SkQ1 had no effect on the lifespan of either males or females in reproductive pairs. Mortality among females was higher than among males irrespective of SkQ1 treatment, this being related to higher costs of reproduction in females. However, SkQ1 accelerated breeding in pairs in the first half of the reproductive period of a year. Although there were no statistical differences in body mass of males and females between experimental and control animals during most of their life, SkQ1-receiving males had higher body mass at the end of their life. The opposite tendency was characteristic for old females. One-year-old males and females of the experimental and control groups showed no difference in intensity of immune response to sheep red blood cells. The dermal hypersensitivity response to phytohemagglutinin (test for T-cell immunity) was significantly higher in SkQ1-treated 1- and 1.5-year-old males. This was not true for females. There was a tendency toward increased density of the neutrophil population in blood in 1-year-old SkQ1-treated males. However, experimental males showed no difference from control males in the activity of the "peroxidase-endogenous hydrogen peroxide system" of neutrophils. The background level of stress estimated by the concentration of cortisol in blood serum was significantly lower in the SkQ1-treated males during autumn adaptive adjustment of the organism. A similar trend was also observed during the January frosts, when the background level of stress was rather high. We observed no differences between cortisol concentration in experimental and control animals during the reproductive period in early spring and mid-summer. We tend to interpret the absence of geroprotective effect of SkQ1 on free-breeding dwarf hamsters by its ability to intensify breeding. We previously demonstrated the ability of SkQ1 to increase the lifespan of non-breeding females.
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