Document Detail

In vivo oocyte hydration in Atlantic halibut (Hippoglossus hippoglossus); proteolytic liberation of free amino acids, and ion transport, are driving forces for osmotic water influx.
MedLine Citation:
PMID:  11821487     Owner:  NLM     Status:  MEDLINE    
The in vivo swelling and hydration of maturing oocytes of Atlantic halibut Hippoglossus hippoglossus were studied in order to characterise the osmotic mechanism underlying oocyte hydration in oviparous marine teleosts that spawn pelagic eggs. Sequential biopsies from two females, spanning four hydration cycles, were examined by osmometry, solute analysis and electrophoresis of dissected hydrating oocytes and ovulated eggs. The hydration cycle of the biopsied halibuts lasted 33-54 h. The majority of ovarian oocytes existed in a pre-hydrated condition (individual wet mass approx. 3.7 mg, diameter approx. 1.87 mm, 63 % H(2)O) with easily visible, non-coalesced, yolk platelets. Group-synchronous batches of the pre-hydrated oocytes increased in individual wet mass, diameter and water content to reach the ovulated egg stage of approximately 15 mg, 3.0 mm and 90 % H(2)O, respectively. The yolk osmolality of the hydrating oocytes was transiently hyperosmotic to the ovarian fluid (range 305-350 mOsmol l(-1)) with a peak osmolality of about 450 mOsmol l(-1) in oocytes of 6-8 mg individual wet mass. The transient hyperosmolality was well accounted for by the increase in oocyte content of free amino acids (FAAs; approx. 2300 nmol oocyte(-1)), K(+) (approx. 750 nmol oocyte(-1)), Cl(-) (approx. 900 nmol oocyte(-1)), total ammonium (approx. 300 nmol oocyte(-1)) and inorganic phosphate (P(i); approx. 200 nmol oocyte(-1)) when relating to the increase in cellular water. The oocyte content of Na(+) did not increase during the hydration phase. Extensive proteolysis of yolk proteins, in particular a 110 kDa protein, correlated with the increase in the FAA pool, although the latter increased by approx. 20 % more than could be accounted for by the decrease in the oocyte protein content. Both indispensable and dispensable amino acids increased in the FAA pool, and particularly serine, alanine, leucine, lysine, glutamine and glutamate. Taurine content remained stable at approx. 70 nmol oocyte(-1) during oocyte hydration. The results show that final hydration of Atlantic halibut oocytes is caused by an osmotic water uptake in which FAAs, derived mainly from the hydrolysis of a 110 kDa yolk protein, contribute approximately 50 % of the yolk osmolality and ions (Cl(-), K(+), P(i), NH(4)(+)) make up the balance.
Roderick Nigel Finn; Gunn C Østby; Birgitta Norberg; Hans Jørgen Fyhn
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of experimental biology     Volume:  205     ISSN:  0022-0949     ISO Abbreviation:  J. Exp. Biol.     Publication Date:  2002 Jan 
Date Detail:
Created Date:  2002-01-31     Completed Date:  2002-04-29     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0243705     Medline TA:  J Exp Biol     Country:  England    
Other Details:
Languages:  eng     Pagination:  211-24     Citation Subset:  IM    
Department of Zoology, University of Bergen, Allégaten 41, N-5007 Bergen, Norway.
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MeSH Terms
Amino Acids / metabolism*
Flounder / physiology*
Ion Transport*
Oocytes / physiology*
Osmolar Concentration
Phosphates / metabolism
Quaternary Ammonium Compounds / metabolism
Water / metabolism*
Reg. No./Substance:
0/Amino Acids; 0/Phosphates; 0/Quaternary Ammonium Compounds; 7732-18-5/Water

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

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