fisiología y biofísica del transporte de agua y solutos - osvaldo chara 1 physiology and...

Fisiología y Biofísica del Transporte de agua y solutos - Osvaldo Chara

1

Physiology and Biophysics of water and solutes transport

*Departamento de Fisiología y Biofísica (Facultad de Medicina, Universidad de Buenos Aires), Buenos Aires, Argentina.(www.fmed.uba.ar)*Instituto de Física de Líquidos y Sistemas Biológicos(Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de la Plata, Comisión de Investigaciones Científcias de la Provincia de Buenos Aires), La Plata, Argentina.(www.iflysib.unlp.edu.ar)*CienciaNet(www.ciencianet.com.ar)

Osvaldo Chara

[email protected]@iflysib.unlp.edu.ar


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Transport of water and solutes…

Transport of non electrolytes: Fick's laws

The cup of coffee of Quilmes

coffee

sugar


4


sugar

coffee




5


sugar

coffee




6


sugar

coffee




7


What did it happen?



8


The phenomenological explanation

Imaginary membrane of area A and length x

Js



9


Cx

ADJ s

s

A very beautiful equation!



10


Now let see another phenomenon:

How is the solute movement across a biological membrane?



11


x

A

C1 C2

Water + solute Water + solute



12


Suppose that both, water and solute can move across the membrane

we will focus on the solute transport (Be patient: we will go to study water transport in 17 min)



13


Suppose that C1 > C2



14


x

C2C1

A



15


Now, we will measure the transport of solute from one side to another



16


x

C2C1

A

Js12

Js12



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(Remember, C1 > C2)

Which is the highest? (Js12 or Js

12)



18


x

C2C1

A

Js12

Js12

Yeah!



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2121 sss JJJ

But what is the relation among Js’s?



20


The beautiful expression:

21 CCx

ADC

x

ADJ ss

s



21

The concept of permeability

Cx

ADJ s

s

But we must to know the length x of the membrane.



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Third week: Bioenergetics


CA

J s

The researchers of physiology and biophysics measure Js/A and C


23


CPA

Js

s

Then, to achieve an equality…



24


x

DP s

s

Therefore…



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Do you remember an electrical circuit?


R


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x

A

C1 C2

Water + solute Water + solute



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Suppose that water can move across the membrane

we will focus on the water transport (great!)

Suppose that solute can not move across the membrane



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Suppose that C1 > C2



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x

C2C1

A



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A phenomenological law of osmosis

v f w i oJ p AV k c c



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Apical membrane

Basolateral membrane

Paracelular path Transcelular path

Acuaporinabicapa lipídica CotransportadorAcuaporinabicapa lipídica CotransportadorAcuaporinaAcuaporinaAcuaporinabicapa lipídica Cotransportador



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Difussion - Partition

Finkelstein, 1987

Range of Posm < 10-3 cm.s-1

Verkman, 2000

Lipidic bilayer



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Water channels: Aquaporins

BA

H2N

HOOC

C

C2

61 5 43

lumen

citoplasma

C

C2

61 5 432

61 5 43

lumen

citoplasma

lumen

citoplasma

A

C

C2

61 5 43

lumen

citoplasma

A

K

A

NP

P

A

N

C

C2

61 5 432

61 5 43

lumen

citoplasma

lumen

citoplasma

B

K

A

NP

P

A

N

H2N

HOOC

H2N

HOOC

K

A

NP

P

A

N



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Acuaporina Localización celular y/o tisular Acuaporina Localización celular y/o tisular

AQP 0 Ojo AQP 7 Riñón

Testículo

Espermatozoides

AQP 1 Glóbulos rojos:

Riñón

Ojo

Cerebro

Pulmón

Endotelio capilar

Oído

Músculos: Esquelético, cardíaco, y liso

AQP 8 Testículo

Espermatozoides

Páncreas

Hígado

Placenta

AQP 2 Riñón AQP 9 Leucocitos

Hígado

Bazo

Óvulos / espermatozoides

Cerebro

AQP 3 Riñón

Tráquea

AQP 10 Duodeno, yeyuno

AQP 4 Riñón

Cerebro

Pulmón

AQP 11 Riñón, hígado

AQP 5 Glándula salival y lacrimal AQP 12 Acino Pancreático

AQP 6 Riñón


Water channels: Aquaporins



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Range of Posm:

(10-3 - 10-1) cm.s-1

Verkman, 2000

n

APp osm

f

Permeability by unit channelFinkelstein, 1987Water channels:

Aquaporins



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Water channels: Aquaporins AQPs!



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Na+-Glutamate (EAAT1)

Na+/glucose (SGLT)

Na+-K+-2Cl- (NKCC)

Cotransports



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versus

¿Cotransporter water-solute? Molecular water pump?

Zeuthen 2002; Hamann y col, 2005

¿Local osmosis?

Duquette y col, 2001

Range of Posm 10-3 cm.s-1

Hamann y col, 2005

Cotransporters



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Transport of electrolytes: Nernst equation

electrolytes



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electrolytes

zoom



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one molecule of electrolyte

zoom




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Let see…

frictional force

electrical force




44

The Flux cvJ d

Then ck

qEJ

Homogeneous concentration!




45

The Flux

Thanks to Einstein we know that

dz

dcDc

k

qEJ

Then

D

Tkk B

Ddz

dc

Tk

qEcJ

B


This is the Nernst-Planck equation



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In equilibrium

Then

0J

Then

cdz

dc

Tk

qE

B

1


dz

dz

cddz

Tk

qE zz

B 00

ln



47

Then


0

ln0 c

zcdzE

Tk

q z

B

dz

dVE

z

EdzV0

zc

cV

Tk

q

B

0ln

But…

zc

c

q

TkV B 0

ln

The Nernst equation!



48


2

1ln12 C

C

ZF

RTV


Ups! The Nernst equation in a physiology book looks different!


49

Transport of electrolytes: Goldman equation

dz

dVzFUc

dz

dcURTJ

a

V

dz

dV

Assuming …

This is again the Nernst-Planck equation

And …

bs cc



50

a

VzFUc

dz

dcURTJ

ac

c

a

JaV

zFcU

dcRTUdz

00


Then …

Integrating …



51

RT

zFV

RT

zFV

ie

e

ecc

a

zFVUJ

1

be

se cc b

isi cc


But remember …

Therefore …



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Osvaldo [email protected]

[email protected]*Departamento de Fisiología y Biofísica (Facultad de Medicina, Universidad de Buenos Aires), Buenos Aires, Argentina.(www.fmed.uba.ar)*Instituto de Física de Líquidos y Sistemas Biológicos(Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de la Plata, Comisión de Investigaciones Científcias de la Provincia de Buenos Aires), La Plata, Argentina.(www.iflysib.unlp.edu.ar)*CienciaNet(www.ciencianet.com.ar)

Thank you!


fisiología y biofísica del transporte de agua y solutos - osvaldo chara 1 physiology and...

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