The effect of modification of mixed function oxidases and inhibition of enterohepatic circulation on concentration of estrogens in plasma in laying hens (Gallus domesticus)
Chen, Shu-Wen
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/23249
Description
Title
The effect of modification of mixed function oxidases and inhibition of enterohepatic circulation on concentration of estrogens in plasma in laying hens (Gallus domesticus)
Author(s)
Chen, Shu-Wen
Issue Date
1992
Doctoral Committee Chair(s)
Dziuk, Philip J.
Department of Study
Animal Sciences
Discipline
Animal Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Health Sciences, Toxicology
Biology, Animal Physiology
Language
eng
Abstract
The rate of metabolism and recirculation contributes to the rate of excretion and to concentration in the circulation. Steroids are substrates for mixed function oxidases (MFO). Enterohepatic circulation (EHC) of estrogens prolongs the half life of estrogens. Thus, the amount of recirculation and the extent of inactivation of estrogens by MFO can influence the peripheral concentration of estrogens. The objective of this thesis was to determine the influence of altering MFO by xenobiotics and inhibition of EHC on the peripheral concentration of estrogens and on estrogen dependent functions in laying hens (Gallus domesticus).
The first objective was to investigate the extent of EHC on peripheral concentration of estrogen in laying hens. Analysis of bile from hens, showed that more than 95% of estrogen are conjugates indicating that the excretion of estrogen conjugates in the bile and indicates the possibility of EHC of estrogen. Sequestering of free estrogens in the gut by oral charcoal leading to fecal excretion or inhibition of bacterial deconjugating enzymes in the gut by antibiotics would reduce reabsorption and recirculation. Oral antibiotics reduced the concentration of estrone (E1) and estradiol glucuronide in the hepatic portal vein. Hen treated with charcoal also had lower concentration of E1 in the hepatic portal vein, and higher circulating concentration of E2 than control hens. Hens treated with charcoal and antibiotics laid more eggs than control hens. The second objective was to investigate the effect of modification of metabolizing enzymes on the peripheral concentration of estrogens in laying hens. Phenobarbital (PB) increased MFO thereby depressing concentration of E2 and E1 but not estrogen conjugates. Treatment with PB increased MFO, decreased E2 and total blood calcium in a dose dependent manner. Depressing MFO by administration of carbon tetrachloride increased the concentration of E2. The third objective was to examine the hypothesis that a change in estrogen in laying hens might detect reproductive toxicants. Aroclor 1254 (PCBs) and Dichlorodiphenyl-trichloroethane (DDT) are reported to have profound effects on avian reproduction, and both caused depression of circulating E2, whereas benzpyrene has been found not to have an affect on reproduction and did not affect E2. High doses of PCBs and PB not only decreased E2 but also depressed reproductive functions such as egg lay, eggshell thickness and total plasma calcium.
These results indicate that effect of diet on reproduction might be due to modification of MFO or inhibition of EHC, and consequent reproduction. It also helped to explain that eggshell thinning and reproductive failure caused by toxicants might be due to change of MFO.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
