INVESTIGADORES
PAFUNDO Diego Esteban
congresos y reuniones científicas
Título:
A new model for ATP release from hypotonically exponed hepatocytes from goldfish.
Autor/es:
PAFUNDO, D. E., CHARA, O. Y SCHWARZBAUM, P. J.
Lugar:
Montevideo, Uruguay
Reunión:
Simposio; VI conferencia internacional de física biológica, V congreso de biofísica del cono sur y XXXIV reunión anual de la Sociedad de Biofísica Argentina; 2007
Resumen:
Nearly all cells possess
mechanisms that enable ATP release in response to hypotonic challenge. Following
cell swelling, extracellular ATP (ATPe) activate specific P
receptors allowing the cell to downregulate its volume towards isotonic values.
This work aimed at
studying the factors governing the kinetics of ATPe of hypotonically
exposed goldfish hepatocytes. Under hypotonicity ATPe is governed by
lytic and non-lytic release of ATP, hydrolysis by ecto-ATPase activity at the
cell surface and diffusion within the extracellular compartment.
We found that
goldfish hepatocytes release ATP after hypotonic shock. The time course of ATPe
is non-monotonic showing a maximum at 725±165 nM (106 cells)-1.
In order to simulate the kinetics of ATPe we developed a one
dimensional mathematical model with three compartments: the intracellular (i),
an extracellular near to the cells membrane (e1), and one representing the bulk
extracellular medium (e2). ATPe is controlled by: 1) non-lytic
release of ATP (JNL), 2) lytic
ATP release, 3) Ecto‑ATPase activity in e1, 4) ATP diffusion between e1 and
e2. JNL was described as a
function JR multiplied by
a function F accounting for a
positive feedback mechanism.
Four JR were tested; i) constant, ii)
step function (JR is zero
until it becomes activated and remains constant thereafter); iii) impulse
function (has the form of a rectangular pulse triggered and shut off at
variable times); iV) a log-normal function which increases non-linearly to a
maximum, followed by a relatively slowly non-linear decrease.
Use of functions
i-iv did not provide a good fit to experimental data. However, using the
log-normal function we simulated the kinetics of ATPe with reasonable accuracy.
The predicted JNL showed
a 1.93 10-18 mol sec-1 peak after 2 sec. The model was also
used to quantify the relative importance of processes 1-4.