Efeitos renais promovidos por polissacarídeos sulfatados da alga marinha Gracilaria cornea

Abstract

The red marine algae are a group of sea live beings able to produce sulfated polysaccharides. These polysaccharides are found in great amount in algae of Gracilaria cornea species and they also have several commercial uses, mainly in industrial fields. They are also used for scientific pourposes because of its biologic activities. This work`s goal is to evaluate the effects of sulfated polysaccharides total (SPTs) from the seaweed Gracilaria cornea contributing to a better understanding about its effects. First, we have studied SPTs effects in three concentrations (1μg/mL, 3μg/mL e 4,5μg/mL), in the renal perfusion system aiming to evaluate the possible changes in kidney parameters. In this experimental model we used male Wistar rats (280-300 g). After the perfusion, the kidneys were subjects of histological analysis. The parameters were analised using ANOVA and Student t-test (p<0,005). The results we have found proved that SPTs promoted a significant increase in perfusion pressure (PP) and in renal vascular resistance (RVR) in concentrations 3,0 and 4,5 µg/mL. The urinary flow (UF) decreased with the 1 µg/mL SPTs concentration, but increased with the 3,0 and 4,5 µg/mL concentrations. The glomerular filtration rate (GFR) significantly dicreased with all the three concentrations. We noticed a decrease in sodium, potassium and chloride transport. The Osmotic Clearance (COSM) decreased with 1,0 μg/mL concentration and increased with 4,5 μg/mL concentration. The histological changes were mild and included tubular and glomerular damages. We also investigated the side effects caused by SPTs in cultured renal tubular cells of the type MDCK (Madin-Darby canine kidney). MDCK cells were grown in plastic flasks at 37 °C in umidified atmosphere of 5% CO2 – air with RPMI 1640 medium supplemented with 10% fetal calf serum. The SPTs caused decrease in cell viability in all studied concentrations (200, 100, 50, 25, 12,5, 6,25 and 3,12 µg/mL) and this effect did not depend on concentration. To evaluate the type of cell death caused by SPTs in MDCK cells, we performed anexin V-FITC and propidium iodide assays, respectively apoptosis and necrosis indicators. This analysis was made in a flow cytometry system with a 50 µg/mL SPTs concentration. We found a significant cell death amount, with apoptotic signs, and also late apoptotic cell death. These findings can improve the understanding about this algae biologic activities and help to find new farmacologic antitumoral weapons.