MARIOARA NICULA, NICOLAE PACALA, LAVINIA STEF, IOAN PET, DOREL DRONCA, ADRIANA GHERBON, MIRELA AHMADI IN VIVO EXPERIMENTS OF NATURAL PRODUCTS PROTECTION OF ANTAGONISTIC EFFECTS OF LEAD ON IRON Living organisms take nutrients from the environment, and together with them, substances with toxic potential – such as heavy metals. Lead is one common metal pollutant especially in aquatic environment, from where the fish can be intoxicated very easily. Bioavailability, distribution, toxic action, synergistic and antagonistic effects are characteristics which can alter the fish health. Our experimental study followed the effects of lead overload in water on iron distribution, in different tissues sample Carassius gibelio Bloch fish. We performed the experiment in four different fish groups: control C; lead – Pb (administration of lead in water 0.075mg/mL of water, as Pb(NO3)2 x ½ H2O); lead (the same dose) and 2% of freeze-dry garlic incorporated into fishes’ food – Pb+garlic; lead (the same dose) and 2% chlorella incorporated into fishes’ food – Pb+chlorella, for 21 consecutive days. The iron concentration was analysed with AAS (Atomic Absorption Spectroscopy) from gills, muscle, skin (and scales), intestine, liver, heart, brain, ovary, testicles, and kidney. The obtained data presented a significantly decrease of iron content in all tested tissue samples that demonstrated, alteration of iron homeostasis, explained by a strong antagonistic effect of lead on iron. Our experiment showed that biologic active principles from garlic and chlorella act like natural protectors, and potentiate the iron deficiency even in the case of lead overload in aquatic environment, for fish.