Effects of long-term heat stress and dietary restriction on the expression of genes of steroidogenic pathway and small heat-shock proteins in rat testicular tissue.

The aim was to investigate the effects of long-term heat stress and dietary restriction on the expression of certain genes involving in steroidogenic pathway and small heat-shock proteins (sHSPs) in rat testis. Sprague Dawley rats (n = 24) were equally divided into four groups. Group I and II were kept at an ambient temperature of 22°C, while Groups III and IV were reared at 38°C for 9 weeks. Feed was freely available for Group I and Group III, while Group II and Group IV were fed 60% of the diet consumed by their ad libitum counterparts. At the end of 9 weeks, testicles were collected under euthanasia. Total RNA was isolated from testis tissue samples. Expression profiles of the genes encoding androgen-binding protein, follicle-stimulating hormone receptor, androgen receptor, luteinising hormone receptor, steroidogenic acute regulatory protein (StAR), cyclooxygenase-2 and sHSP genes were assessed at mRNA levels using qPCR. Long-term heat stress decreased the expression of StAR and HspB10 genes while dietary restriction upregulated StAR gene expression. The results suggested that long-term heat stress negatively affected the expression of StAR and HspB10 genes and the dietary restriction was able to reverse negative effect of heat stress on the expression of StAR gene in rat testis.

Expression profile of interferon tau-stimulated genes in ovine peripheral blood leukocytes during embryonic death.

Early and efficient detection of embryonic death (ED) has a valuable impact as important as early pregnancy diagnosis in ruminants. Among early pregnancy diagnosis methods, detection of the expression of interferon tau-stimulated genes (ISGs) in peripheral blood leukocytes (PBLs) is well documented in cows and ewes. Therefore, we hypothesized that the expression profile of ISGs in PBLs might also be useful for detecting ED in these animals. For this purpose, pregnant ewes were used as an experimental model. Pregnancy was detected on Day 18 after mating by transrectal ultrasonography. Pregnant ewes were divided into a control group (sham injection on Day 18, n = 10) and ED group (treated with 75 µg synthetic PGF2α on Day 18, n = 12). PBLs and plasma were collected on Days 0 (mating day), 15, 18, 19, 20, 21, 23, and 25 by jugular venipuncture. Total RNA was isolated from PBLs. ISGs expression levels were determined by real-time polymerase chain reaction in triplicate. Electrochemiluminescence immunoassay was used to measure progesterone (P4) levels in plasma. In the ED group, the P4 level declined to less than 1 ng/mL on Day 19 and remained at a low level until the end of the study. Compared with that on Day 0, receptor transporter protein 4 (RTP4) and ISG15 expression was upregulated on Day 15 and remained high until Day 21 in both groups, and RTP4 and ISG15 mRNA levels were attenuated on Days 23 and 25 only in the ED group (P < 0.001). Myxovirus resistance 1 expression was upregulated on Day 15 and remained high until Day 23 in both groups, but was attenuated on Day 25 in the ED group (P < 0.05). The B2-microglobulin mRNA level did not change significantly during the study in either group. These results indicate that the decline in P4 concentration was an immediate response to PGF2α and that the embryo may have survived longer than the CL on the basis of the extended period of ISGs expression. This suggests that the absence of P4 could be the reason for ED rather than a direct effect of PGF2α. In conclusion, the expression of ISGs, including ISG15, RTP4, and myxovirus resistance 1, but not B2-microglobulin, in PBLs may serve as a marker of ED.

Comparison of endocrine and cellular mechanisms regulating the corpus luteum of primates and ruminants.

The corpus luteum (CL) is a transient endocrine organ that is essential for maintenance of pregnancy in both ruminants and primates. The cellular and endocrine mechanisms that regulate the CL in these species have commonalities and some distinct and intriguing differences. Both species have similar cellular content with large luteal cells derived from the granulosa cells of the follicle, small luteal cells from follicular thecal cells, and large numbers of capillary endothelial cells that form the vasculature that has an essential role in optimal CL function. Intriguingly, the large luteal cells in ruminants grow larger than in primates and acquire a capacity for high constitutive progesterone (P4) production that is independent of stimulation from LH. In contrast, the primate CL and the granulosa lutein cells from primates continue to require stimulation by LH/CG throughout the luteal phase. Although the preovulatory follicle of women and cows had similar size and steroidogenic output (10 to 20 mg/h), the bovine CL had about ten-fold greater P4 output compared to the human CL (17.4 vs. 1.4 mg/h), possibly due to the development of high constitutive P4 output by the bovine large luteal cells. The continued dependence of the primate CL on LH/CG/cAMP also seems to underlie luteolysis, as there seems to be a requirement for greater luteotropic support in the older primate CL than is provided by the endogenous LH pulses. Conversely, regression of the ruminant CL is initiated by PGF from the nonpregnant uterus. Consequently, the short luteal phase in ruminants is primarily due to premature secretion of PGF by the nonpregnant uterus and early CL regression, whereas CL insufficiency in primates is related to inadequate luteotropic support and premature CL regression. Thus, the key functions of the CL, pregnancy maintenance and CL regression in the absence of pregnancy, are produced by common cellular and enzymatic pathways regulated by very distinct luteotropic and luteolytic mechanisms in the CL of primates and ruminants.