Laboratory of Fish Laboratory of Fish Endocrinology and Endocrinology and

Environmental PhysiologyEnvironmental Physiology

Hawaii Institute of Marine Hawaii Institute of Marine BiologyBiology

School of Ocean and Earth School of Ocean and Earth Science and TechnologyScience and Technology

University of HawaiUniversity of Hawai`̀ii

The PeopleThe People• Tetsuya HiranoTetsuya Hirano• Three postdoctoralsThree postdoctorals

Andy PierceAndy PierceLori Davis Lori Davis Marc MetienMarc Metien

• Four graduate studentsFour graduate studentsEli WittEli WittJason BrevesJason BrevesAnna KosztownyAnna KosztownyMasatomo YoshiokaMasatomo Yoshioka

The Neuroendocrine System: The Neuroendocrine System: the interface between the the interface between the

organism and its organism and its environmentenvironment

•How do fish adapt to changing How do fish adapt to changing environmental conditions?environmental conditions?

•How do fish exploit resources?How do fish exploit resources?•How do fish optimize their use of How do fish optimize their use of

energy?energy?•How do fish optimize the timing of How do fish optimize the timing of

important events and processes?important events and processes?•How do human activities impact the How do human activities impact the

biology of fish?biology of fish?

Why HIMBWhy HIMB

•Availability of pristinely clean Availability of pristinely clean warm seawaterwarm seawater

•Proximity to California and JapanProximity to California and Japan•Access to coral reef and coastal Access to coral reef and coastal

fish species fish species •Association with SOESTAssociation with SOEST• I/R appointmentI/R appointment

Current ProjectsCurrent Projects•OsmoreceptionOsmoreception•Endocrine disruptionEndocrine disruption•Regulation of growth, Regulation of growth,

development and osmoregulation, development and osmoregulation, and energy investment into those and energy investment into those processesprocessesTeleost fishTeleost fishElasmobranch fishElasmobranch fish

•Regulation of egg developmentRegulation of egg development•Regulation of immune responseRegulation of immune response•Fishmeal-free fish feedsFishmeal-free fish feeds

FundingFunding• EPAEPA• Two NSFTwo NSF• Four USDA CREESFour USDA CREES• ~ $8-9 hundred thousand~ $8-9 hundred thousand

OutputOutput• ~ 150 peer-refereed publications ~ 150 peer-refereed publications • Twenty-eight previous postdoc’s and Twenty-eight previous postdoc’s and

graduate studentsgraduate students• Over eighty undergraduate studentsOver eighty undergraduate students• A substantial number of high school A substantial number of high school

studentsstudents

Regulating Salt and Water Regulating Salt and Water BalanceBalance

•Involves a large portion of the neuroendocrine system

•Involves sensors that monitor, and in turn, regulate salt and water balance

““One of the most troublesome of One of the most troublesome of all problems in clinical all problems in clinical medicine is maintenance of medicine is maintenance of adequate body fluids and adequate body fluids and proper balance between the proper balance between the extracellular and intracellular extracellular and intracellular fluid volumes in seriously ill fluid volumes in seriously ill patients.”patients.”

Arthur C. Guyton

Osmoregulation: Osmoregulation: The Challenge!The Challenge!

•OsmoregulationOsmoregulation typically accounts for 25-50% of the non-swimming energy budget in fish.

•Hormones and other Hormones and other chemical messengers of chemical messengers of the neuroendocrine the neuroendocrine systemsystem facilitate the adaptation of euryhaline fish to changing salinities by regulating the activity of osmoregulatory mechanisms.

Hyperosmotic

Hyposmotic

THE REALITY: Under physiological conditions cells adapt to changes in extracellular osmolality by adjusting intracellular solute composition to regulate their volume.

Why osmoregulation?Why osmoregulation?THE TEXTBOOK: When exposed to an osmotic challenge, cells burst or shrivel:

““Life is all about the Life is all about the interaction between interaction between

molecules.”molecules.”Linus Pauling

The real reason The real reason for for osmoregulation:osmoregulation:

Importance of Importance of OsmoregulationOsmoregulation

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

(Modified from Neil Campbell, 1998)

•The functional structure of macromolecules is maintained by weak forces

The Reason: the complex structure and arrangement of most osmoreceptors Sites of vasopressin

synthesis

Brain

Pituitary gland

Site of vasopressin secretion

Little is known about the neuroendocrine mechanisms that control osmoregulation.

The prolactin cells of the The prolactin cells of the rostral pars rostral pars distalisdistalis of teleost fish provide an of teleost fish provide an excellent model for studying excellent model for studying osmoreception.osmoreception.

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

RPD

Tilapia Prolactin Cells Appear To Be Osmoreceptors

Extracellular osmolality

Prolactin

Prolactin cells (osmoreceptors)

Rostral pars distalis

Methods

RPD1. Dissection

2. OvernightPre-

incubation

3. Cell dispersio

n

4. Applicati

on to chamber

FURA2----AM

AM ester cleaved by natural esterases

FURA2----Ca2+

340 nm

380 nm 505 nm

FURA2

FURA2

FURA2----AM

Measuring Intracellular Free Calcium

PR

L (

% c

han

ge)

Cell v

olu

me

(% c

hange)

Osmolality (mOsmolal)

304050

100

200

300

400500

250300

350400

90

95

100

105110

Relationship between extracellular osmolality, cell volume and prolactin

release.

Summary

1.1. The rise in prolactin release in response to a decrease The rise in prolactin release in response to a decrease in extracellular osmolality is closely tied to an increase in extracellular osmolality is closely tied to an increase in cell size.in cell size.

2.2. Hyposmotically-induced prolactin release is dependent Hyposmotically-induced prolactin release is dependent on the inward movement of extracellular Caon the inward movement of extracellular Ca2+2+..

1. Inward movement of H2O

PRL releasePRL release

Extracellular osmolality

2. increase in cell volume

3) Extracellular Ca2+ entry

PRL Cell

Thank You