Document Detail

Steroidogenic correlates of pregnancy in the rock hyrax (Procavia capensis).
MedLine Citation:
PMID:  11324711     Owner:  NLM     Status:  MEDLINE    
In pregnant rock hyraxes isolated leucocytes metabolise both [3H]pregnenolone and [3H]progesterone while whole blood, erythrocytes and an erythrocyte/leucocyte mixture only metabolised [3H]progesterone. Plasma displayed no tendency to metabolically convert any one of these two steroids. In whole blood [3H]progesterone appears to be converted to 5alpha-pregnane-3,20-dione and a compound with chromatographic properties similar to that of 5alpha-pregnan-3alpha-ol-20-one. 5Alpha-pregnane-3,20-dione exhibited a high relative binding affinity for the uterine progesterone eceptor (94%), but 5alpha-pregnan-3alpha-ol-20-one displayed very little affinity for the same receptor (0.4%). 5Alpha-pregnane-3,20-dione may therefore aid in the maintenance of pregnancy. Corpora lutea metabolised progesterone to 17alpha-hydroxyprogesterone, a compound exhibiting no progestational function because of its low relative binding affinity for the uterine progesterone receptor (2%). Progesterone appears to be the main product of the corpus luteum. However, 5alpha-pregnane-3,20-dione circulated at concentrations approximately 8.5 times higher than progesterone, probably due to the metabolic conversion of progesterone to 5alpha-pregnane-3,20-dione by the blood. We conclude that in the hyrax progesterone, produced by the corpora lutea, enters the circulation, where it is reduced to 5alpha-pregnanes. 5Alpha-pregane-3,20-dione may then be transported to the uterus where it binds to the progesterone receptor to assist in the maintenance of pregnancy. This mechanism appears to be analogous to that of the African elephant which is phylogenetically related to the hyrax, except that in the elephant the 5alpha-reduced metabolites are produced by luteal tissue and not the blood.
S Kirkman; E D Wallace; R J van Aarde; H C Potgieter
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Life sciences     Volume:  68     ISSN:  0024-3205     ISO Abbreviation:  Life Sci.     Publication Date:  2001 Mar 
Date Detail:
Created Date:  2001-04-27     Completed Date:  2001-05-17     Revised Date:  2003-11-14    
Medline Journal Info:
Nlm Unique ID:  0375521     Medline TA:  Life Sci     Country:  England    
Other Details:
Languages:  eng     Pagination:  2061-72     Citation Subset:  IM    
Department of Zoology & Entomology, University of Pretoria, South Africa.
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MeSH Terms
Binding, Competitive
Cells, Cultured
Chromatography, High Pressure Liquid
Corpus Luteum / metabolism
Erythrocytes / cytology,  metabolism
Hyraxes / physiology*
Leukocytes / cytology,  metabolism
Pregnancy, Animal / blood*
Pregnanediones / blood
Pregnenolone / blood*
Progesterone / blood*
Receptors, Progesterone / metabolism
Reg. No./Substance:
0/Pregnanediones; 0/Receptors, Progesterone; 145-13-1/Pregnenolone; 566-65-4/5-alpha-Dihydroprogesterone; 57-83-0/Progesterone

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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