Laboratory of Fish Endocrinology and Environmental Physiology

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Laboratory of Fish Endocrinology and
Environmental Physiology
Hawaii Institute of Marine Biology School of
Ocean and Earth Science and Technology University
of Hawaii
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The People

• Tetsuya Hirano
• Three postdoctorals
• Andy Pierce
• Lori Davis
• Marc Metien
• Four graduate students
• Eli Witt
• Jason Breves
• Anna Kosztowny
• Masatomo Yoshioka

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The Neuroendocrine System the interface between
the organism and its environment

• How do fish adapt to changing environmental
  conditions?
• How do fish exploit resources?
• How do fish optimize their use of energy?
• How do fish optimize the timing of important
  events and processes?
• How do human activities impact the biology of
  fish?

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Why HIMB

• Availability of pristinely clean warm seawater
• Proximity to California and Japan
• Access to coral reef and coastal fish species
• Association with SOEST
• I/R appointment

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Current Projects

• Osmoreception
• Endocrine disruption
• Regulation of growth, development and
  osmoregulation, and energy investment into those
  processes
• Teleost fish
• Elasmobranch fish
• Regulation of egg development
• Regulation of immune response
• Fishmeal-free fish feeds

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Funding

• EPA
• Two NSF
• Four USDA CREES
• 8-9 hundred thousand

Output

• 150 peer-refereed publications
• Twenty-eight previous postdocs and graduate
  students
• Over eighty undergraduate students
• A substantial number of high school students

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Regulating Salt and Water Balance

• Involves a large portion of the neuroendocrine
  system
• Involves sensors that monitor, and in turn,
  regulate salt and water balance

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Osmoregulation The Challenge!
One of the most troublesome of all problems in
clinical medicine is maintenance of adequate body
fluids and proper balance between the
extracellular and intracellular fluid volumes in
seriously ill patients.
Arthur C. Guyton
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• Osmoregulation typically accounts for 25-50 of
  the non-swimming energy budget in fish.
• Hormones and other chemical messengers of the
  neuroendocrine system facilitate the adaptation
  of euryhaline fish to changing salinities by
  regulating the activity of osmoregulatory
  mechanisms.

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Why osmoregulation?
THE TEXTBOOK When exposed to an osmotic
challenge, cells burst or shrivel
THE REALITY Under physiological conditions cells
adapt to changes in extracellular osmolality by
adjusting intracellular solute composition to
regulate their volume.
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The real reason for osmoregulation
Life is all about the interaction between
molecules.
Linus Pauling
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Importance of Osmoregulation

• The functional structure of macromolecules is
  maintained by weak forces

• A stable internal osmotic environment is
  essential to the maintenance of the structure,
  and therefore, the function of macromolecules.

(Modified from Neil Campbell, 1998)
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Little is known about the neuroendocrine
mechanisms that control osmoregulation.
The Reason the complex structure and arrangement
of most osmoreceptors
Brain
Pituitary gland
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The prolactin cells of the rostral pars distalis
of teleost fish provide an excellent model for
studying osmoreception.

• Conservatively, 95-99 of the rostral pars
  distalis is comprised of prolactin cells.

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Tilapia Prolactin Cells Appear To Be Osmoreceptors
Extracellular osmolality
Rostral pars distalis
Prolactin cells (osmoreceptors)
Prolactin
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Measuring Intracellular Free Calcium
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Relationship between extracellular osmolality,
cell volume and prolactin release.
500
400
300
200
PRL ( change)
100
50
110
40
105
30
Cell volume ( change)
100
250
95
300
350
90
400
Osmolality (mOsmolal)
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Summary

1. The rise in prolactin release in response to a
   decrease in extracellular osmolality is closely
   tied to an increase in cell size.
2. Hyposmotically-induced prolactin release is
   dependent on the inward movement of extracellular
   Ca2.

3) Extracellular Ca2 entry

1. increase in cell volume

PRL Cell

1. Inward movement of H2O

PRL release
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Thank You