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Title: Progesterone and estradiol plasma levels in neonatally irradiated cycling rats

Abstract

Female rats which were exposed to a single low dose of gamma irradiation (6R or 15R) at the age of 8 days produce smaller litters when mature than untreated controls. The possibility that the impaired fertility resulted from altered ovarian activity as reflected by changes in plasma levels of progesterone or estardiol was investigated. Plasma levels of both steroids were determined throughout the day of proestrus. Progesterone level was also determined in 6R animals on the day of weaning. The maturity of such irradiated rats was assessed by observing the time of vaginal opening. The results indicated that the preovulatory peak of progesterone was delayed in the 6R rats whereas in the 15R group its levels were significantly lower. On the other hand no differences in estradiol plasma levels were noticed between the groups. The higher level of progesterone in the 6R animals was not evident on the day of weaning and was even in both groups, but vaginal opening in the irradiated rats was significantly delayed. The elevated level of progesterone might be responsible, among other endocrine changes, for the lower fertility of neonatally irradiated mature female rats.

Authors:
;  [1]
  1. (Nuclear Research Center-Negev, Beer-Sheva (Israel))
Publication Date:
OSTI Identifier:
7062127
Resource Type:
Journal Article
Resource Relation:
Journal Name: Endocrine Research; (USA); Journal Volume: 16:2
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; ESTRADIOL; BIOSYNTHESIS; GAMMA RADIATION; TERATOGENESIS; PROGESTERONE; ACUTE IRRADIATION; ESTROUS CYCLE; FEMALES; FERTILITY; LOW DOSE IRRADIATION; NEONATES; OVARIES; RATS; WHOLE-BODY IRRADIATION; ACUTE EXPOSURE; ANIMALS; BODY; ELECTROMAGNETIC RADIATION; ESTRANES; ESTROGENS; EXTERNAL IRRADIATION; FEMALE GENITALS; GONADS; HORMONES; HYDROXY COMPOUNDS; IONIZING RADIATIONS; IRRADIATION; KETONES; MAMMALS; ORGANIC COMPOUNDS; ORGANS; PREGNANES; RADIATIONS; RODENTS; STEROID HORMONES; STEROIDS; SYNTHESIS; VERTEBRATES; 560152* - Radiation Effects on Animals- Animals

Citation Formats

Freud, A., and Sod-Moriah, U.A. Progesterone and estradiol plasma levels in neonatally irradiated cycling rats. United States: N. p., 1990. Web. doi:10.1080/07435809009033001.
Freud, A., & Sod-Moriah, U.A. Progesterone and estradiol plasma levels in neonatally irradiated cycling rats. United States. doi:10.1080/07435809009033001.
Freud, A., and Sod-Moriah, U.A. Mon . "Progesterone and estradiol plasma levels in neonatally irradiated cycling rats". United States. doi:10.1080/07435809009033001.
@article{osti_7062127,
title = {Progesterone and estradiol plasma levels in neonatally irradiated cycling rats},
author = {Freud, A. and Sod-Moriah, U.A.},
abstractNote = {Female rats which were exposed to a single low dose of gamma irradiation (6R or 15R) at the age of 8 days produce smaller litters when mature than untreated controls. The possibility that the impaired fertility resulted from altered ovarian activity as reflected by changes in plasma levels of progesterone or estardiol was investigated. Plasma levels of both steroids were determined throughout the day of proestrus. Progesterone level was also determined in 6R animals on the day of weaning. The maturity of such irradiated rats was assessed by observing the time of vaginal opening. The results indicated that the preovulatory peak of progesterone was delayed in the 6R rats whereas in the 15R group its levels were significantly lower. On the other hand no differences in estradiol plasma levels were noticed between the groups. The higher level of progesterone in the 6R animals was not evident on the day of weaning and was even in both groups, but vaginal opening in the irradiated rats was significantly delayed. The elevated level of progesterone might be responsible, among other endocrine changes, for the lower fertility of neonatally irradiated mature female rats.},
doi = {10.1080/07435809009033001},
journal = {Endocrine Research; (USA)},
number = ,
volume = 16:2,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 1990},
month = {Mon Jan 01 00:00:00 EST 1990}
}
  • The human breast cancer cell line MCF-7 responds to estrogens with increased progesterone receptor (PR) levels. In this study, we use dense amino acid density shift analyses to address directly the question of whether estrogen increases PR levels in MCF-7 cells by altering rates of receptor synthesis and/or degradation. Using different concentrations of estradiol (E2), which achieve PR levels that are half-maximal (3 X 10(-11) M F2) or maximal (6 X 10(-11) M E2), we have done sucrose gradient density shift analyses using dense (/sup 15/N, /sup 13/C, /sup 2/H) amino acid incorporation to study rates of PR synthesis andmore » degradation. These studies reveal a nonlinear loss of preexisting normal density receptor with time. From kinetic modeling analyses, equivalent rates of degradation are estimated for PR whether maximal or half-maximal levels are maintained, indicating that the major effect of E2 on PR content is to increase the rate of PR synthesis while leaving the degradation rate unaltered. The E2-stimulated increase in PR protein is also associated with increased levels of PR mRNA, as demonstrated by the use of a human PR cDNA probe. These density shift data provide evidence that the increased PR levels after estrogen exposure in MCF-7 cells are the result of an increased rate of receptor synthesis, rather than modulation of the rate of receptor degradation.« less
  • Female rats which were exposed to a single low dose of gamma irradiation (6R or 15R) at the age of 8 days produce smaller litters when mature than untreated controls. In order to study the possibility that such an impaired reproductive performance could result from a reduced ovulation rate, neonatally irradiated females were treated with PMSG (12 iu/rat) at the age of 26 days. Another group of rats, similarly treated, was further injected with hCG (5 iu/rat) 48 hours later. Animals were killed 48, 55, 60 and 72 hours after PMSG treatment or 72 and 120 after hCG injection. Themore » results indicated that PMSG treatment increased the ovarian weight of non-irradiated controls as well as of irradiated rats and in all animals induced a proestrus like profile of LH. Only a combined treatment of PMSG and hCG resulted in ovulation and corpora lutea formation with significantly increased numbers of corpora lutea in the ovaries of the irradiated rats. The latter was associated with higher progesterone plasma levels not correlated to the number of corpora lutea. The gradual decrease in the number of ovarian binding sites for hCG with increased radiation dose and the increased association constant in the 15R group could not explain the increased sensitivity of the ovary to exogenous gonadotropins which results from neonatal exposure to low doses of gamma irradiation.« less
  • X-irradiation of the rat brain (1000R, at two days of age), suppresses the normal age-related increase in the weight of the cerebellum and cerebral hemispheres and influences amino acid levels. The decrease in glutamic acid concentration, particularly in the cerebellum, supports the previously advanced proposition that this amino acid may be associated with or may be the transmitter of, the rat cerebellar granule cells. Subfractionation of the cerebellar tissue reveals that the decrease in the glutamic acid level consequent to the loss of granule cells, is reflected in the cytoplasmic fraction but not in the synaptic vesicle subfraction, where glutamicmore » acid was increased. The reduced weight gain in the cerebral hemispheres after irradiation, is accompanied by a significant decrease of aspartate in the cytoplasmic fraction, changes which suggest that a specific cell type, with aspartic acid as its neurotransmitter (possibly in the hippocampus), may also be radiosensitive in the early postnatal period. In contrast, in the synaptic vesicle fraction from cerebral hemispheres, all free amino acids, with the exception of glutamine, increased significantly. Overall, the changes in free amino acid concentration induced by X-irradiation in the cytoplasmic fraction in both brain regions studied are opposite to those found in the synaptic vesicle fraction and although they may indicate changes in specific cell populations, as proposed above, they could also reflect changes in cellular compartmentalization and metabolism or changes in the relative axonal arborization of the affected regions.« less