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Volume 7, Issue 3, June Issue - 2019, Pages:329-334

Authors: El-Masry KA, El-Fouly HA, Gabr SA
Abstract: The objective of present study was to determine the pattern and impact of pregnancy stage on the concentrations in serum estradiol-17β (E2-17β), testosterone hormones and immunoglobulin G (IgG). For this purpose, blood samples were collected from 16 crossbred, pregnant, lactating cows at the intervals of each two weeks. From these collected samples, serum hormone concentration was determined by Radioimmunoassay (125I-RIA) technique and IgG concentration was assayed by using the method involves antigen diffusing radially. Results of present study revealed that concentration of E2-17β is insignificant from 1st to the 4th month of gestation and tended to increase from the 4.5th month to the end of gestation. After parturition E2-17β returned to its normal level on 30th day of postpartum. Further, concentration of testosterone hormone start increasing  (29.76 pg/ml) from the 4th month, after this it gradually increased (P <0.01) with the advances of gestation (185.40 pg/ml) up to the 9th month, thereafter testosterone level reached to the peak (197.80 pg/ml) at the end of pregnancy as compared to the average during non-pregnancy period. Concentration of IgG remained at basal level from the 1st to 6.5th month of gestation that averaged 23.65 g/l. Thereafter a sharpest increase in IgG level was occurred up to the 8.5th month that followed by a depression in the subsequent period until parturition. It can be concluded that concentrations of E2-17β and testosterone remained at low levels around the 4th – 5th month and progressively increased and showing a sharp rise in the 9.3 month of gestation. Moreover, the levels of IgG insignificantly changed until the 6.5th month of pregnancy and a sharpest rise occurred in the 8.5th month of gestation.
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Full Text: 1 Introduction Changes in hormones concentration and functioning during pregnancy period of ruminants have been widely studied by various researchers (Al-Anbaky, 2009; Harichadan et al., 2014). Among these, estrogen is essential hormones which help in maintain pregnancy and initiation of parturition. Further, Estradiol-17β stimulates the synthesis of endometrial oxytocin receptors and reduce the rate of LH releases which is must for the maintain progesterone production during early pregnancy (Peters & Ball, 1995). The important roles of E2-17β and testosterone hormone during pregnancy period may be attributed to that the biochemical reactions for the formation of these hormones are the same, and the male sex hormone testosterone can serve as precursor for the synthesis of E2-17β and their pathway involving the conversion of testosterone to E2-17β is more significant in the ovary (Tietz, 1982). Moreover, during pregnancy period, feto-placental tissues appears to be the major site of estrogens biosynthesis was able to convert testosterone to E2-17β in the basal membrane of theca cells (Tietz, 1982; Solomon, 1994; Peters & Ball, 1995). Estrogen plays an essential role in the maintenance of pregnancy and initiation of parturition (Peters & Ball, 1995). On the other side, testosterone hormone may modify placental function and had an effect on transport of nutrients to the fetus (Carlsen et al., 2006). Concerning the IgG levels, Janeway et al. (2002) reported that IgG is the main immunoglobulin in the blood system accounting for approximately 80% of the total circulating immunoglobulin, whereas its function is to bind pathogenic agents and induce an immune response. According to Harichandan et al. (2014), the relationship between testosterone hormone and each of E2-17β and IgG may induce the high production of steroid hormones throughout pregnancy course, but a wide discrepancy and changes in these items have been reported by Min et al. (2002), Carlsen et al. (2006) and Al-Anbaky (2009). The present study was therefore undertaken to determine the changes in the general profile of E2-17β, testosterone and IgG concentrations throughout pregnancy as compared with non-pregnancy period of cows. 2 Materials and Methods A total of 16 crossbred (Brown Swiss 50% and Balady 50%) pregnant and lactating cows, approximating 4-5 years of age and weighing 340±20 kg were used for current study and changes in E2-17β, testosterone as well as IgG levels during pregnancy period were studied in detail. The animals were in moderate milking ability during postpartum period and observed daily for estrus and considered to be in estrus when they stood to be mounted by another cows. Then, jugular blood samples were collected from these non-pregnant cows and were considered as samples for control period. Natural mating with pure Brown Swiss bull was carried out for all cows. Records of breeding dates were maintained. Blood samples were collected from all mated cows from the 1st days of mating and continued throughout pregnancy at the intervals of two weeks. Trans rectal palpation of the reproductive tract on day 60 of post mating was used as a pregnancy test. The animals were fed on concentrated diets (17% crude protein, 2.5% ether extract and 16.5% crude fiber) according to their trimester of pregnancy. The animals had free access to graze green forage throughout pregnancy period. Trace elements mixtures (Pfizer Co.) were added daily for all animals by 1.5 g/kg dry matter. Drinking water and rice straw were offered freely ad lib. The concentrations of E2-17β and testosterone hormones were determined by radioimmunoassay technique (Elbanna et al., 1988 ) using solid phase coated tubes kits purchased from diagnostic systems laboratories Inc., Webstir, Texas, USA. Serum IgG concentration was measured using kit for IgG of the Binding Sit Limited Co., Birmingham, UK. Statistical analysis of the obtained data were carried out, whereas the differences between mean values of the items of non-pregnancy period (control period) and each of mean values of pregnancy period of cows were tested by paired "t" test according to Snedecor & Cochran (1994). 3 Results and Discussion Data presented in Tables 1 and Figure 1 showed that E2-17β concentrations varied from 32.31 pg/ml (during non-pregnancy period) to 37.12pg/ml (in the 4th month of gestation) and the difference between these two means was found insignificant. Thereafter, the concentration of E2-17β increased (P<0.01)              to 38.67 and 42.64 pg/ml in the 4.5th and 5th month of gestation, respectively. In the 5.5th month of pregnancy E2-17β concentrations increased (P<0.01) progressively with the advance of gestation and reach maximum (248.86 pg/ml) at the end of pregnancy course. Findings of present study are associated with the data of previous studies, whereas the concentrations of estrone and E2-17β in bovine blood plasma remain low during the early period of gestation and gradually increased throughout mid, to late gestation (Hung & Prakash, 1990; Patel, 1999). Similarly, El-Fouly et al. (1998a) showed that E2-17β levels in crossbred cows did not change in the 1st trimester while it significantly increased in the 2nd trimester and increased sharply at the end of the 3rd trimester of gestation, reached to its peak on day 1 before calving. Mekonnin et al. (2017) conducted a study for estradiol level detection in pregnant heifers and cows. In both cows and heifers, higher estradiol concentrations were recorded during the first trimester of pregnancy as compare to other stages of pregnancy. Similarly, Opara et al. (2006) reported higher level of estradiol in pregnant heifers as compared to estrus or other reproductive conditions (anestrus or diestrus) and in this situation findings of present study are in agreement with these earlier reports. Hirako et al. (2003) reported that during the 1st trimester of gestating cows, E2-17β remained at basal levels until day 80, followed by an increase in estrone and E217β after day 80 of gestation. Also, Al-Anbaky (2009) suggested that in pregnant cow’s plasma E2 -17β levels varied from 9 pg/ml (in the first third of pregnancy) to 282.60 pg/ml (during the last month of gestation).Similar findings were reported by El-Masry et al. (1997) in a study conducted on Egyptian buffaloes. Several potential mechanisms affect the level of E2-17β during the pregnancy period, whereas the concentration of fetal cortisol from fetal adrenals helps in E2-17β releases from placenta (Gitau et al., 2005). Further, the conversion of testosterone hormone into E2-17β held at the granulosa cells by the action of aromatase (Peters & Ball, 1995; Hirako et al. 2003). Also, sex of fetus and the levels of progesterone hormone might also associate with the releases and concentration of E2-17β (EL-Fouly et al., 1998 b). The higher levels of E2-17β during third trimester of pregnancy have evoked normal development of mammary alveolar tissues which might be involved in the primary myometrium and triggering the prostaglandin release in farm animals; this would help in further myometrium contractions (Peters & Ball, 1995). A combination of all these mechanisms is also conceivable. Functions of testosterone hormone throughout pregnancy period have been well reported previously, this hormone induce the production of plasma progesterone binding proteins during pregnancy which help in maintaining high progesterone levels (Wyk et al., 1994). Maternal testosterone may also cross the placenta and exert a direct effect on fetal growth and / or energy homeostasis (Carlsen et al., 2006) as well as testosterone with estrogen accelerates blood flow to the uterus during parturition (Min et al., 2002). In results of present study, testosterone concentration remained at basal levels (23.92 pg/ml) until the 3.5th month of gestation, thereafter testosterone level began to increase (P<0.01) progressively with the advance of gestation and a sharpest rise recorded 197.80 pg/ml in the 9.3th months of gestation (Tables 1 and Figure 2). These results are associated with finding of by Gaiani et al. (1984) who found that plasma testosterone levels in cows ranged between 20 to 50 pg/ml until about 90 days of pregnancy, then it increase progressively to about 220pg/ml around 270 days of gestation. Moreover, Al-Anbaky (2009) revealed that testosterone levels in cows were 0.32 ng/ml in the 3rd month of gestation, increase to 0.541 ng/ml at the end of 8th month of gestation. Similarly, Emara (2015) reported that non-pregnant cows have low level of testosterone (0.08 ng/ml) and showed a continuous gradual increase throughout pregnancy period till day 3-7 of prepartum (0.28 mg/ml), followed by a drop on 30th day of postpartum which averaged 0.097 and  0.06 ng/ml, respectively. Similar findings were reported by Peters &Ball (1995) and Al-Anbaky (2009). According to these researchers this gradually augmentation in the level of testosterone at advance stage of gestation may be attributed to the biosynthesis and excretion of testosterone hormone by several sources such as placental tissues, ovary, mammary gland and fetal males. As shown in tables 1 and figure 3, serum IgG levels showed insignificant fluctuation from the 1st month of the 6.5th months of gestation. Thereafter, IgG increased sharply in the subsequent months and it reached to the peak in the 8.5th months, followed by the depression in IgG levels in the 9th and 9.3th months of gestation. General trend of IgG levels throughout pregnancy period are in agreement with the findings of Carolina et al. (2014) in domestic animals and by Malek et al. (1996) in woman; these researchers reported that fetal IgG begins to increase from 13 to 18 weeks of gestation and this improvement continuously increases till the end of final trimester and typically exceed the maternal IgG concentrations. This increases in globulin level with the advance of gestation might be due to change in their endocrine profile, since an animal's transition occurs from non-gravid to gravid state and their transformation might have influenced more production of globulin by B-lymphocytes (Harichandan et al., 2014). In addition, high circulating levels of estrogen during pregnancy course (El-Fouly et al., 1998 a; Patel, 1999; Hirako et al., 2003) and glucocorticoids near the onset of parturition can suppress important lymphocyte function (Levkut et al., 2002). Concerning the depression in IgG at postpartum period; Herr et al. (2011) revealed that plasma IgG level recovered by the 4th week of postpartum and the extent of IgG reduction seemed to be depended on the initial IgG concentration. Such reduction in immunoglobulin concentration at the terminal stage of pregnancy in cows might have occurred because the transition of globulin fraction from the blood to the mammary gland and tubular genital tract (Liberg,1977; Harichandan et al., 2014). From the results of present study it can be concluded that interaction and changes in the levels of E2-17 β and testosterone hormones were augmented and coincided with the advance of gestation for sustenance of pregnancy, showing higher concentrations during the late months of pregnancy compared to non-pregnancy ones, and the levels of IgG insignificantly changed until the 6.5th months of pregnancy and a sharpest rise occurred in the 8.5th months of gestation. Conflict of Interest The authors declare that there is no conflict of interest in this manuscript.

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