Some Events of Thyrotropin-Releasing Hormone Metabolism Are Regulated in Lactating and Cycling Rats
18
Citation
0
Reference
10
Related Paper
Citation Trend
Abstract:
Levels of thyrotropin-releasing hormone (TRH), TRH mRNA and pyroglutamyl peptidase II were analyzed in the hypothalamus-adenohypophyseal axis during lactation and estrous cycle. Mediobasal hypothalamic levels of TRH dropped 41% (p < 0.01) from pregnancy levels (taken as 100%) on the first day of lactation, recovering until day 15 to the values observed at pregnancy. A sharp decrease was also observed during weaning (36%, p < 0.01 compared to last day of lactation). TRH levels in the neurohypophysis increased during lactation and dropped at weaning. Highest TRH mRNA levels in the paraventricular nucleus were found at the end of pregnancy and beginning of lactation; they decreased 37% (p < 0.05) at day 5 of lactation and stayed constant thereafter. Pyroglutamyl peptidase II adenohypophyseal activity was not modified during lactation but changed during estrous cycle. Relative to estrous values, activity diminished 58% (p < 0.05) at 10.00 h (57% at 14.00 h) during diestrus 2 and 27% at 10.00 h (37% at 14.00 h) during proestrus. Hypothalamic TRH mRNA levels fluctuated in an opposite manner to adenohypophyseal pyroglutamyl peptidase II during the estrous cycle with a peak at diestrus 2: 183% of the estrous value (p < 0.05). These data point to a regulation of TRH metabolism in conditions where prolactin (PRL) secretion fluctuates. They also suggest a sharp release of TRH between the end of pregnancy and the first day of lactation and that translational efficiency or post-translational processing of TRH precursor in the paraventricular neurons (projecting to the median eminence) increases during lactation and drops at weaning, concomitantly with PRL secretion.Norepinephrine has been assayed in the hypothalamus of rats during different phases of the estrous cycle. The content of catecholamine in the anterior and middle hypothalamus was minimal at estrus, rose significantly during diestrus, and reached maximal levels during proestrus. In the posterior hypothalamus no significant changes were detected. (Endocrinology81: 1405, 1967)
Cite
Citations (86)
To ascertain the changes of vaginal cells at different stages of estrous cycle in Duolang sheep,vaginal smear method was used in five Duolang sheep with a normal estrous cycle,and the vaginal smear samples were collected and continuously observed by microscopic examination for 20 days.The results showed that the vaginal cells were mainly composed of keratinocytes,nucleated epithelial cells,and leukocytes.Keratinocytes constituted the majority in estrus,and there were no significant differences(P0.05) among three kinds of cells with similar number in metestrus;most of the cells were leukocytes in diestrus;most of the cells were nucleated epithelium cells in proestrus.According to the changes in cell types,the estrous cycle was determined,it was found that the duration of the different stages was as follows: metestrus(4±1)d,diestrus(9±3)d,proestrus(16±3)d,and estrus(2±1)d.It is indicated that the vaginal smear method can accurately determine the different stages of estrous cycle in Duolang sheep.
Vaginal smear
Cite
Citations (0)
Cite
Citations (18)
Effects of growth hormone-releasing hormone (GRH) and corticotropin-releasing hormone (CRH) on the release of immunoreactive thyrotropin-releasing hormone (ir-TRH) from the rat hypothalamus in vitro were studied. The rat hypothalamus was incubated in medium 199 with 1.0 mg/ml of bacitracin (pH 7.4) for 20 min. The amount of ir-TRH release into the medium was measured by radioimmunoassay. The ir-TRH release from the rat hypothalamus was inhibited significantly in a dose-related manner with the addition of GRH or CRH. These findings suggest that GRH and CRH inhibit ir-TRH release from the rat hypothalamus in vitro.
Corticotropin-releasing hormone
Thyrotropin-releasing hormone receptor
Growth hormone–releasing hormone
Cite
Citations (11)
Intramuscular injection
Cite
Citations (6)
Age at puberty in gilts and the number of days from weaning to estrus were determined on 132 gilts and 370 primiparous sows. The average age at puberty was 197.5 ± 1.8 (SE) days, in a range of 141 to 254 days. In this study, Yorkshire sows averaged 5.5 ± 0.3 days and Lacombe sows 14.3 ± 0.8 days to estrus after weaning (P < 0.001). In the first week after weaning, 90.5% of the Yorkshire sows and 48.0% of the Lacombe sows returned to estrus. One Yorkshire sow (0.5%) and 35 Lacombe sows (20.2%) failed to show estrus by 28 days after weaning. Yorkshire females had an average estrous cycle length of 21.0 ± 0.2 days, and Lacombe females 21.7 ± 0.1 days (P < 0.05).
Cite
Citations (29)
The experiment observed the estrous cycle of twenty-five mice with two vagina smear methods .The mice whose estrous cycle were regular were cheese to handle with superovulation method. According to the different periods (estrus,post-estrus,interestrus ),these mice classified into three test groups, and then other thirteen mice that were unknown estrous cycle were contrast group. The results showed that : (1) The method 2 was better than method 1, the method 2 had little effect to the estrous cycle of the mice. (2) The superovulation results of the interestrus mice were the best of all other periods. The rates of the valuable embryos and embryos quantity were significantly better than the estrus,post-estrus and unknown estrous cycle.
Cite
Citations (0)
Tea normal volunteers received 100 to 800 ug of TRH intravenously. Serum prolactin was measured by a specific radioimmunoassay before and at intervals after TRH administration. Serum prolactin began to rise within 5 minutes and was maximal after 15 to 20 minutes. The mean peak response at 15 minutes was 11 times the fasting level. Serum prolactin had returned to the baseline by 180 minutes. It is concluded that TRH may be closely related to prolactin releasing factors in crude hypothalamic extracts.
Serum concentration
Cite
Citations (315)
Prolactin cell
Cite
Citations (21)