Identification and properties of steroid-binding proteins in nesting Chelonia mydas plasma

Ikonomopoulou, MP, Bradley, AJ, Whittier, JM and Ibrahim, K (2006) Identification and properties of steroid-binding proteins in nesting Chelonia mydas plasma. Journal of Comparative Physiology B, 176 8: 775-782. doi:10.1007/s00360-006-0099-2


Author Ikonomopoulou, MP
Bradley, AJ
Whittier, JM
Ibrahim, K
Title Identification and properties of steroid-binding proteins in nesting Chelonia mydas plasma
Formatted title
Identification and properties of steroid-binding proteins in nesting Chelonia mydas plasma
Journal name Journal of Comparative Physiology B   Check publisher's open access policy
ISSN 0174-1578
1432-136X
Publication date 2006-11
Sub-type Article (original research)
DOI 10.1007/s00360-006-0099-2
Volume 176
Issue 8
Start page 775
End page 782
Total pages 8
Editor Gerhard Heldmaier
Place of publication Berlin, Germany
Publisher Springer-Verlag
Collection year 2006
Language eng
Subject C1
270604 Comparative Physiology
770304 Physical and chemical conditions
0601 Biochemistry and Cell Biology
0606 Physiology
1116 Medical Physiology
Formatted abstract
We report for the first time the presence of a sex steroid-binding protein in the plasma of green sea turtles Chelonia mydas, which provides an insight into reproductive status. A high affinity, low capacity sex hormone steroid-binding protein was identified in nesting C. mydas and its thermal profile was established. In nesting C. mydas testosterone and oestradiol bind at 4°C with high affinity (Ka = 1.49 ± 0.09 × 109 M−1; 0.17 ± 0.02 × 107 M−1) and low binding capacity (Bmax = 3.24 ± 0.84 × 10−5 M; 0.33 ± 0.06 × 10−4 M). The binding affinity and capacity of testosterone at 23 and 36°C, respectively were similar to those determined at 4°C. However, oestradiol showed no binding activity at 36°C. With competition studies we showed that oestradiol and oestrone do not compete for binding sites. Furthermore, in nesting C. mydas plasma no high-affinity binding was observed for adrenocortical steroids (cortisol and corticosterone) and progesterone. Our results indicate that in nesting C. mydas plasma temperature has a minimal effect on the high-affinity binding of testosterone to sex steroid-binding protein, however, the high affinity binding of oestradiol to sex steroid-binding protein is abolished at a hypothetically high (36°C) sea/ambient/body temperature. This suggests that at high core body temperatures most of the oestradiol becomes biologically available to the tissues rather than remaining bound to a high-affinity carrier.
© Springer-Verlag 2006
Keyword Physiology
Zoology
Binding proteins
Green sea turtles
Chelonia mydas
Sex steroids
High-affinity binding
Chrysemys-picta
Green turtles
Reproductive-cycle
Rainbow-trout
Bufo-arenarum
Sea-turtle
Globulin
Progesterone
Testosterone
Q-Index Code C1

 
Available Versions of this Record
 
Versions
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 3 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 4 times in Scopus Article | Citations
Google Scholar Search Google Scholar
Created: Wed, 15 Aug 2007, 07:59:35 EST