Modificación de la actividad citoplasmática de la fosfatasa alcalina intestinal de la rata en presencia de calcio

BRANCE MARÍA LORENA; BRUN LUCAS; RIGALLI ALFREDO; PUCHE RODOLFO

Rosario

Congreso; VI Congreso y XXIV Reunión Científica anual; 2004

Sociedad de Biología de Rosario

In vitro, the activity of AP exhibits a biphasic response to calcium (Ca++): it increases at Ca++ concentrations lower than 10 mM, and decreases if concentration of Ca++ is greater than 20 mM. In vivo, Ca++ produces an increase in brush border activity of enterocytes but decreases the activity in the cytosol. The aim of this work was to study changes in cytoplasmic activity of AP by modification of cytosolic concentrations of Ca++. Female adult rats IIM/FcM  were used in the experiments. 3 cm of duodenum were isolated in situ by mean of two ligatures. A catheter was inserted and it was used to flow 2 ml of the following solutions into the lumen: Group A and B: NaCl 150 mM; Group C and D: CaCl2 50 mM + NaCl 150 mM; Group E: CaCl2 50 mM + NaCl 150 mM + calcium ionophore A23187 0.4 mM. Within 20 min the duodenum was extracted, fixed, parattin embedded and samples were sectioned at 10 mm. Sections of groups B y D were exposed to EDTA 500 mM and CaCl2 50 mM for 30 and 20 min, respectively. AP activity was put in evidence by incubation with 5-Br-4-Cl-3-indolyl phosphate. The activity in cytosol was measured as absorbance units on digital images. Values were analyzed by one-way ANOVA. Mean±SD are shown in the table. Differences were considered significant if p<0,05. The same letter indicates differences between groups Group n mUnits of absorbance Comparison among groups A   4 78±32 a, b B 4 5.2±8.7 a C   4 39±26 b, c, d D   4 103±45 c E  4 81±45  d AP activity in the cytosol of enterocyte decreases as a function of luminal Ca++. This effect could be caused by a decrease in the concentration of the ion in the aforementioned compartment.