The role of genotype, social stress, and season of the year in regulation of hormonal function of murine testis in vitro

Micropopulations consisting of six male mice of different genotypes were studied (each of lines A/He, CBA/Lac, C57BL/6J, DD, YT, and PT was represented by one male). Interlinear differences in the level of social dominance and the effects of genotype, social hierarchy, and season on in vitro testosterone production by testes were examined under different incubation conditions. The testosterone production was estimated under control conditions and under stimulation with human chorionic gonadotropin (CG). Significant genetic differences in the initial and CG-stimulated testosterone production by testes incubated in vitro were found. By the control production, the genotypes fell into two groups: lines C57BL/6J, A/He, and CBA/Lac had low production of the hormone; lines YT, PT, and DD, high production. By responsiveness of gonads to CG, the genotypes fell into three groups: line CBA/Lac had low testosterone production by testes; lines C57BL/6J, A/He, YT, and DD, line PT, intermediate production; and line PT, high production. The obtained data indicate stability of genetic polymorphism for the responsiveness of testes to gonadotropins, because neither season nor the formation of social hierarchy could significantly change the interlinear differences. In line PT characterized by high hormonal activity of gonads in the control and under stimulation with gonadotropins, males became dominant in a significantly greater number of cases studied during the formation of hierarchy in micropopulations. The dynamics of both control production of a male sex hormone and responsiveness of testes to CG was established in vitro during the formation of social hierarchy; the effects of season on this dynamics were revealed. Specific characteristics of secretory activity of testes were detected in the control and under stimulation with gonadotropins, depending on incubation conditions. Seasonal and genotypic characteristics of the responsiveness of testes to CG were revealed under different incubation conditions. Genotypic characteristics indicate interlinear differences in the degree of inertia of testosterone biosynthesis on exposure to gonadotropins.     

Effect of genotype and social stress on cAMP- and substrate-dependent mechanisms of regulating hormonal function of testis in mice]

Several steps of cAMP- and substrate-dependent testosterone production in the testes were studied with laboratory mouse micropopulations of six inbred strains (A/He, CBA/Lac, C57BL/6J, DD, YT, PT). The strains differed in basal testosterone production in the gonads and in its response to activation of the adenylate cyclase signal transduction pathway at various steps by human chorionic gonadotropin (hCG), the cholera toxin, forskolin, and dibutyryl-cAMP and in the presence of pregnenolone, an early precursor of testosterone. Establishment of dominant-subordinate relationships in mouse populations substantially affected testosterone production in response to all activators of testicular steroidogenesis. The secretory activity of the testes decreased at the early establishment of social hierarchy in experimental micropopulations, then returned to the initial level, and again decreased in the case of activation with hCG, dibutyryl-cAMP, and pregnenolone. With all activators of steroidogenesis, basal and activated testosterone production changed in the same direction during the establishment and maintenance of social hierarchy, suggesting coordinated changes in all examined steps of testosterone biosynthesis in the testes. The among-strain differences in response to all activators of steroidogenesis remained much the same at various stages of the establishment of social hierarchy. The parameters of cAMP- and substrate-dependent testosterone production averaged over individual stages of the establishment of social hierarchy proved associated. Their genotypic correlations were positive and, in many cases, significant. Subsequent component analysis showed that one principal component accounted for more than 80% of the total among-strain variation, suggesting a coordinated genetic control of the endocrine function of the testes.     

The Effects of the Genotype and Social Stress on cAMP- and Substrate-Dependent Mechanism Regulating the Hormone-Producing Function of Mouse Testes

Several steps of cAMP- and substrate-dependent testosterone production in the testes were studied with laboratory mouse micropopulations of six inbred strains (A/He, CBA/Lac, C57Bl/6J, DD, YT, PP). The strains differed in basal testosterone production in the gonads and in its response to activation of the adenylate cyclase signal transduction pathway at various steps by human chorionic gonadotropin (hCG), the cholera toxin, forskolin, and dibutyryl-cAMP and in the presence of pregnenolone, an early precursor of testosterone. Establishment of dominant–subordinate relationships in mouse populations substantially affected testosterone production in response to all activators of testicular steroidogenesis. The secretory activity of the testes decreased at the early establishment of social hierarchy in experimental micropopulations, then returned to the initial level, and again decreased in the case of activation with hCG, dibutyryl-cAMP, and pregnenolone. With all activators of steroidogenesis, basal and activated testosterone production changed in the same direction during the establishment and maintenance of social hierarchy, suggesting coordinated changes in all examined steps of testosterone biosynthesis in the testes. The among-strain differences in response to all activators of steroidogenesis remained much the same at various stages of the establishment of social hierarchy. The parameters of cAMP- and substrate-dependent testosterone production averaged over individual stages of the establishment of social hierarchy proved associated. Their genotypic correlations were positive and, in many cases, significant. Subsequent component analysis showed that one principal component accounted for more than 80% of the total among-strain variation, suggesting a coordinated genetic control of the endocrine function of the testes.     

Effect of Genotype on Formation of Hormonal Function of Leydig Cells during Mouse Postnatal Development

Changes in in vitro testosterone production by Leydig cells induced by chorionic gonadotropin, dibutyryl-cAMP, and pregnenolone have been studied during postnatal development of four inbred mouse strains BALB/c, PT, CBA/Lac, and A/He, with contrast hormonal activity of testes in sexually mature males. The interlinear differences significantly change with age of the males by all studied indices indicating genotype-dependent formation of hormonal activity of Leydig cells during postnatal development. Coordinated interlinear variability between all indices of Leydig cells reactivity has been established for each studied period of postnatal development. Hence, we have established coordinated interlinear genetic variability of hormonal function of Leydig cells, which was confirmed by considerable changes in it during postnatal development at puberty. Definitive genotypic differences in hormonal activity of Leydig cells appeared by late pubertal and early postpubertal development (day 60) and coincided with termination of morphological differentiation of Leydig cells and appearance of the differentiated cell population.     

Phenogenetic analysis of testicular responsiveness to chorionic gonadotropin in inbred mouse strains

Genetic differences in the testicular hormonal responsiveness to in vivo administration of chorionic gonadotropin (CG) between adult male mice of eight inbred strains (A/Sn, CBA/Lac, CC57Br, C57Bl/6J, DBA/2J, GR, PT, and YT) were determined. In addition, the genetic variation of the body and testis weights was estimated as related to the responsiveness to stimulation of steroidogenesis with CG. Adult males were subcutaneously injected with 10 IU of CG or physiological saline 120 min before decapitation. It was found that the baseline testosterone level in the blood serum and its content in the testes only slightly varied in males of the strains studied. Administration of CG increased these parameters by a factor of 3–45, depending on the strain. The results of the study indicate genetic differences in the testicular reactivity to CG. In addition, it has been found that the response to administration of CG, as compared to the baseline levels, provides the most reliable information on the genetic characteristics of the hormonal potential of the testes. The given set of inbred mouse strains may be a promising genetic model for studying the physiological and hereditary variations of testicular steroidogenesis.     

Effect of genotype on hormonal function formation of Leydig cells during mouse postnatal development

Changes in in vitro testosterone production by Leydig cells induced by chorionic gonadotropin, dibutyryl-cAMP, and pregnenolone have been studied during postnatal development of four inbred mouse strains BALB/c, PT, CBA/Lac, and A/He, with contrast hormonal activity of testes in sexually mature males. The interlinear differences significantly change with age of the males by all studied indices indicating genotype-dependent formation of hormonal activity of Leydig cells during postnatal development. Coordinated interlinear variability between all indices of Leydig cells reactivity has been established for each studied period of postnatal development. Hence, we have established coordinated interlinear genetic variability of hormonal function of Leydig cells, which was confirmed by considerable changes in it during postnatal development at puberty. Definitive genotypic differences in hormonal activity of Leydig cells appeared by late pubertal and early postpubertal development (day 60) and coincided with termination of morphological differentiation of Leydig cells and appearance of the differentiated cell population.     

Social domination and reproductive success in male laboratory mice (Mus musculus)

The task of the present study was to evaluate effect of social status and of genotype on success of reproduction of male laboratory mice with use of ethological model of social hierarchy of “minimal socium”. The model represents the paired maintenance of two male mice of different genotypes (PT and CBA/Lac). The mice resided for 30 days in one experimental cage and established between them the dominant-subordinant relations. After this, each pair of males was supplemented by two DD/He females. Regardless of their genotype, the dominants became fathers more often than the subordinants and left more offspring. It has been established that the complete suppression of fertility did not occur. It is suggested that this allows them to make genetic contribution to the next generation and to remain in the genetic pool of population.     

Mouse Leydig Cells with Different Androgen Production Potential Are Resistant to Estrogenic Stimuli but Responsive to Bisphenol A Which Attenuates Testosterone Metabolism

It is well known that estrogens and estrogen-like endocrine disruptors can suppress steroidogenic gene expression, attenuate androgen production and decrease differentiation of adult Leydig cell lineage. However, there is no information about the possible link between the potency of Leydig cells to produce androgens and their sensitivity to estrogenic stimuli. Thus, the present study explored the relationship between androgen production potential of Leydig cells and their responsiveness to estrogenic compounds. To investigate this relationship we selected mouse genotypes contrasting in sex hormone levels and differing in testosterone/estradiol (T/E₂) ratio. We found that two mouse genotypes, CBA/Lac and C57BL/6j have the highest and the lowest serum T/E₂ ratio associated with increased serum LH level in C57BL/6j compared to CBA/Lac. Analysis of steroidogenic gene expression demonstrated significant upregulation of Cyp19 gene expression but coordinated suppression of LHR, StAR, 3βHSDI and Cyp17a1 in Leydig cells from C57BL/6j that was associated with attenuated androgen production in basal and hCG-stimulated conditions compared to CBA/Lac mice. These genotype-dependent differences in steroidogenesis were not linked to changes in the expression of estrogen receptors ERα and Gpr30, while ERβ expression was attenuated in Leydig cells from C57BL/6j compared to CBA/Lac. No effects of estrogenic agonists on steroidogenesis in Leydig cells from both genotypes were found. In contrast, xenoestrogen bisphenol A significantly potentiated hCG-activated androgen production by Leydig cells from C57BL/6j and CBA/Lac mice by suppressing conversion of testosterone into corresponding metabolite 5α-androstane-3α,17β-diol. All together our data indicate that developing mouse Leydig cells with different androgen production potential are resistant to estrogenic stimuli, while xenoestrogen BPA facilitates hCG-induced steroidogenesis in mouse Leydig cells via attenuation of testosterone metabolism. This cellular event can cause premature maturation of Leydig cells that may create abnormal intratesticular paracrine milieu and disturb proper development of germ cells.     

Growth and development peculiarities of testicles in postpubertal period in inbred mice lines PT and CBA/Lac

The goal of this study is to perform a comparative genetic investigation of testicle development during the postpubescence period (from days 70 to 90 of life) in the inbred mice lines PT and CBA/Lac. Interlinear differences in the body and testicular weight, serum testosterone concentration, number of epididymal spermatozoa, area of testicular epithelium, semeniferous tubule lumen, and insulae of Leydig cells were analyzed. It was found that the morphological and histomorphometric parameters of testicles in males from the PT line compared to the males of the CBA/Lac line did not reach a definitive stage with the end of the post-pubescence period and kept on developing until day 90 of life. Therefore, genetic differences remain in the postpubertal testicular development of laboratory mice.     

Interlinear differences in generative function formation in pubescence of male mice

The formation of generative function in pubescence is studied in males of three inbred mice lines BALB/cLac, CBA/Lac, and PT. From days 35 through 60 of life every 5 days the amount of sperm cells and the quantity of abnormal heads of spermatozoa in males are calculated in both epididymises and the morphometry of the testicles, epididymises, and seminal vesicles is carried out. Interlinear deviations in the pubertal dynamics of the parameters of spermatogenesis and the morphometric indexes are determined, indicating a weak spermatogenesis process in males of CBA/Lac in comparison with males from the other lines. Males from the line CBA/Lac are characterized by a low amount of epididymal spermatozoa combined with low frequency of abnormal spermatozoon heads; these traits can be considered as a compensatory process that increases fertility. By the end of the period, i.e., on days 55–60 of life, the males of all three inbred mice lines have not reached the definitive level in the number of epididymal spermatozoa; the weight of the testicles, epididymise, and seminal vesicles; and body weight. Thus, in laboratory mice, the beginning of reproductive activity is not connected with these reproductive indexes reaching the definitive level. The results of the study show that in adult mature males of laboratory mice the interlinear deviations in generative function emerge in the pubertal period and persist thereafter.     

Phenotypic variation of spermatogenesis and a search for associations with genetic polymorphism in 13 inbred mouse strains

Adult mice of the BALB/cLac, PT, CBA/Lac, DD/He, A/He, SWR, NZB, GR, DBA/2J, CC57Br, C57Bl/6J, A/Sn, and YT inbred strains were tested for the count, motility, and morphology of sperms from the caudal region of the epididymis. The protein-coding regions of the cytochrome P450 aromatase (CYP19a1), estrogen receptor 2 (ESR2), steroidogenic factor 1 (Nr5a1), and sex-determining (Sry) gene were sequenced. A substantial genetic heterogeneity for the genes was observed, as well as a phenotypic variation in spermatogenetic parameters, but the variation was rather discordant. The specifics of the interstrain variation in spermatogenetic parameters indicated that a physiological compensatory mechanism increases certain spermatogenetic parameters when other ones are low to maintain male fertility at a level sufficient for successful reproduction. For instance, a high sperm production compensated for a low sperm motility in DD/He males. In the issue of the protein-coding sequencing of the analyzed genes, 16 various mutations were observed. The decreases in proportion of motile sperms and in their velocity were attributed to mutations (I63T and W133L) of the Sry gene in the DD/He strain.     

Interstrain differences in testicular responses to hCG: effects of a female exposition

It is known that among many animal species, including laboratory mice, a short-time exposition to a female causes activation of the pituitary-testicular axis in males, which then rapidly decreases. Effects of a prolonged female exposition on the testicular testosterone output in response to hCG injections were investigated in adult males of two inbred mice strains CBA/Lac and PT. The males of both genotypes kept with females for 5 days were injected subcutaneously with 10 IU of hCG 120 minutes before decapitation. Males of the same genotype and similar age keeping alone were served as control. The serum testosterone concentration and its testicular content were measured with immune-enzyme assay. It has been shown that the hCG increased the testosterone concentration and its testicular content in control males of both strains, but the testosterone output was expressed more significantly in PT males in comparison with CBA/Lac. The prolonged exposition of a female itself did not influence the testosterone output in males of both strains. However, it increased significantly the testicular response to hCG in PT strain. The data obtained suggest that a long-term exposition of a female could reinforce the testicular reactivity to hCG in genotype-dependent manner.     

The Role of Genotype in the Formation of Leydig Cell Hormone Function during Postnatal Ontogeny in Diallele Crosses of Laboratory Mice

Production of testosterone by Leydig cells in the postnatal ontogeny during sexual maturation under in vitro stimulation by chorionic gonadotropin, dibutiryl-cAMP, and pregnenolon was studied in males of four inbred mouse lines (BALB/c, PT, CBA/Lac, and A/He) and their F1 reciprocal hybrids. Highly statistically significant association between the animal genotype and age was revealed for all parameters studied, which indicates the genotype-dependent formation of the Leydig cell hormone function during the postnatal ontogeny. The effect of genotype was characterized by two specific features. First, in each postnatal ontogeny stage examined correlative genetic variability of the cAMP- and substrate-dependent Leydig cell responsiveness was observed. Second, during postnatal ontogeny coordinated genetic variability underwent substantial ontogenetic changes. Definite pattern of genetic differences in the Leydig cell hormone activity was formed only at the late pubertal–early post-pubertal stage (60th day after birth). This process coincided with the completion of the Leydig cell morphological differentiation and the appearance of mature cells in the population. Thus, formation of the Leydig cell hormone function during postnatal ontogeny is under coordinated genetic control, which itself undergoes significant changes during sexual maturation.     

Tyrosine hydroxylase activity and expression of its gene in mice with contrasting capacity to dominate in social stress]

Changes of tyrosine hydroxylase (TH) activity and level of mRNA of TH gene in PT and CBA/Lac mouse strains, which are contrast by ability to dominate in heterogenous populations, were investigated. It was established, that the activity of TH both in dominate PT and subordinate CBA/Lac mice in hypothalamus, hippocampus and brain stem elevated in one hour after forming of micropopulations. But the appearance of this increase was different: activation of TH in hypothalamus and brain stem of PT mice was stronger then one in CBA/Lac mice. Moreover, the beginning of the reaction in brain stem of PT mice was earlier then that of CBA/Lac mice. MRNA level of TH gene in hypothalamus and brain stem in one hour was elevated only in PT mice for 50% and 200%, respectively. No changing in expression TH gene was found in hippocampus. In conclusion, it was suggested that the activation of catecholamine biosynthesis under social stress in hypothalamus and brain stem of male mice was due to the TH activation and increase of its gene expression.     

Spermatogenesis parameters and testosterone production at puberty as predictors of testicular functional activity in mice (<Emphasis Type="Italic">Mus musculus</Emphasis>)

The aim of this study was to investigate fertility-associated parameters of spermatogenesis and androgenic status in male laboratory mice at puberty and to assess their prognostic significance in the realization of the definitive testicular function. In three inbred murine strains, BALB/cLac, CBA/Lac and PT, the serum testosterone level, its testicular concentration, epididymal sperm count (sperm reserve) and portion of sperm with abnormal head morphology were evaluated on days 45 (puberty) and 90 (adulthood) of postnatal development. CBA/Lac males were characterized by a lower epididymal sperm count vs. other strains at both ages indicative of poorer spermatogenesis. At the same time, CBA/Lac males had a lower portion of sperm with abnormal head morphology, and this could be considered as a compensatory reaction aimed at improving sperm fertility. Distinct inter-strain differences in the portion of sperm with morphologically abnormal heads were established at both ages, while the inter-strain ratio remained invariable (BALB/cLac > PT > CBA/Lac). Thus, the level of abnormal spermatogenesis in the pubertal period may have a predictive significance for the definitive testicular activity in adult mice. No inter-strain and age-dependent changes were found in serum and testicular testosterone levels except for the PT strain, in which both testosterone levels rose from puberty to adulthood, suggesting a shift of the pubertal testosterone peak towards later times. Our data show that in male laboratory mice the genetic peculiarities of the testicular function manifest themselves during puberty and persist until adulthood.     

Immunological,Cytogenetical, and Behavioral Changes in CBA and C57BL/6 Male Mice after Pheromonal Action

Immunological and cytogenetical changes were studied in mice-recipients of CBA and C57BL/6 lines as well as modifications of their behavior appearing as a result of action of various stressors. Post-stress volatile excretions of CBA males cause led to a pronounced immunosuppression in males-recipients of both lines. This resulted in a decrease of capability for immune response of the stressed mice to sheep erythrocytes. Besides, in young males of the CBA line, frequency of chromosome aberrations in bone marrow cells increased statistically significantly after stressing by syngenec volatile excretions of mature animals. Attractive properties of volatile excretions of the CBA and C57BL/6 line males were studied. In norm, animals of both lines prefer syngenic odors of intact males donors. However, for the CBA line males, post-stress excretions from males-donors of both lines became more attractive than excretions from intact animals. Also revealed were interline differences in incidence of choice of syngenic and allogenic post-stress excretions. This can be explained both by different stress-reactivity of animals-donors and differences of recipients of the studied genotypes in selectivity to olfactory stimuli. An importance of olfactory stresses and of the revealed interline differences for explanation of some micro-and macroevolutionary synecological processes in the domestic mouse is discussed.     

Features of adrenal gland and gonadal reactions in mice with a genetic predisposition to dominance under zoo-social stress]

Intensity and duration of endocrine responses of adrenals and gonads in QT, CBA/Lac male mice and heir first generation reciprocal hybrids (F1) mice, social stress were studied. PT males had higher level of corticosterone in 1 h after stress, the adrenals and gonads reactions being some hrs shorter, as compared with CBA/Lac mice. No differences were observed in dynamics among reciprocal hybrids. They inherited not only high capacity to dominance in micropopulations but also reactions of adrenal activation and gonadal inhibition. Similar results were obtained, when these features were studied in dominant and subordinate males of PT strain mice.     

Experience of defeat increases the susceptibility to catatonic - like state in mice

The ability to develop the catatonic-like state (reflex immobility reaction - RIR) due to stimulation of the skin at the scruff was investigated in mice of two strains — C57BL/6J and CBA/Lac. The total time of immobility and number of paroxysms during test were measured. It has been shown that the number of paroxysms was significantly fewer and the total time of immobility was significantly longer in CBA/Lac strain than in C57BL/6J. In each strain group housed animals as well as submissive ones with successive experience of defeats demonstrated a more expressed immobility than individually housed or aggressive males with successive experience of victories, respectively. Changing the social status in aggressive animals as a consequence of confrontation with aggressive males resulted in the increased immobility in CBA/Lac but not in C57BL/6J mice. The results suggest that the experience of defeat in submissive males is connected with increased ability to develop RIR.     

Effect of genotype on the development of aggressive and submissive behavior in the mouse

Aggressive and submissive behaviour was studied in CBA/Lac and C57BL/6J strains of mice during long-term intermale interaction with syngenic partners. It was shown that the aggressiveness of aggressive C57BL/6J animals was more expressive than that of CBA/Lac' ones. The structure of submissive behaviour of this strains' encounters was also significantly different. Prolonged-defeat experience changed the character of submissive behaviour of C57BL/6J, but not of CBA/Lac' ones. Aggression of dominant animals considerably decreased in both strains. It is suggested that CBA/Lac and C57BL/6J mice had different mechanisms of suppression of intermale aggression.     

The effect of the ACTH(4-10) fragment on certain forms of adaptive behavior in mice of various genetic groups

CBA/Lac/Sto mice, C57/BL/6J mice and random bred mice with robertsonian translocation of chromosomes 8 and 17 (T1IEM mice) were compared under normal conditions and after ACTH4-10 injections. The rate of food procuring learning in U-shaped maze and in radial 5-arm maze was studied, and the ability of mice to extrapolate the direction of stimulus movement. Peptide i. p. injections (40 mkg/kg) stimulated the learning in U-shaped maze in all genotypes. T1IEM mice demonstrated better radial arm maze performance than CBA. Peptide injections tended to improve it in the former and to impair in the latter genotype. T1IEM mice demonstrated the ability for extrapolation, while CBA mice revealed no such ability. ACTH4-10 injections improved problem solving only in T1IEM mice. Cases when animals "refused" to participate in the experiment, were significantly rare in groups of all genotypes under peptide treatment.