Mathematical modelling of water transport across Beta vulgaris storage root plasma membrane vesicles under hyperosmotic challenges

KARINA ALLEVA; OSVALDO CHARA; MOIRA SUTKA; GABRIEL AMODEO

Montenvideo, Uruguay

Congreso; 6th Internacional Conference of Biological Physics, ICBP and 5th Southern Cone Biophysics Congress; 2007

ICBP y Sociedad Argentina de Biofísica

The objective of this work is to further characterize qualitatively and quantitatively water transport pathways across Beta vulgaris storage root plasma membrane vesicles (PMV). Spectroscopy of light scattering under stop flow conditions has been previously used to study the osmotic response of these vesicles to hyperosmotic shock. These results showed that PMV contain aquaporins with high capacity to move water and sensitivity to medium acidification. In order to deep insight these experimental data, mathematical modelling was applied. The model involves the following hypothesis: i) water moves according to an osmotic mechanism across PMV, ii) there are two not necessarily equal water pathways through PMV, iii) there is not solute movement across the PMV. Mathematically, model is characterized by an ordinary non lineal differential equation subject to an initial condition. Simulations were performed using Euler method with a custom made software developed in Visual Basic code. The procedure allows predicting time course of vesicles volume changes following hyperosmotic insult. Our results suggest that kinetics of vesicle volume changes can be explained as the combined response of two different water pathways, one with high water osmotic permeability (HP) and other with low water osmotic permeability (LP), being HP pathway which contributes with approximately 80% of the response. Interestingly, when osmotic shock is performed at acidic pH, LP is the pathway that throws in the greater part of osmotic response. Modelling of water movement in Beta vulgaris plasma membrane vesicles allows better understanding of osmotic water transport phenomena.