Exposure of Rana ridibunda to lead II. Impact of lead on various parameters of liver metabolism of the frog Rana ridibunda

Abstract

There are no data at present on the impact of lead (Pb) on amphibian metabolism, although declines of amphibian populations due to man-made changes in the environment have been recorded in recent years. We studied the impact of Pb on the liver metabolism of the frog Rana ridibunda by measuring the hepatic levels of glycogen, lactate, total fat, protein and glucose. Liver is one of the primary target organs of Pb bioaccumulation. Frogs were exposed for 4, 10 and 30 days to 14 mg l(-1) of Pb (in the form of Pb(NO(3))(2) dissolved in water) and compared with matched controls. The level of glycogen in the liver increased until day 30. The increase of the metabolite was time-dependent because there was a positive correlation (r = 0.994, P = 0.006) between glycogen concentration and the days of Pb exposure. Lactate concentration declined continuously up to day 30. Liver fat content decreased from day 10 to day 30. Protein concentration declined continuously until day 30. Glucose concentration increased up to day 30. Glycogen concentration was correlated negatively with liver fat content (r = -0.474, P = 0.005), liver protein content (r = -0.562, P = 0.0004) and lactate concentration (r = -0.472, P = 0.005), whereas it was correlated positively with the Pb burden of the liver (r = 0.578, P = 0.0005). The frog appeared to face a metabolic stress over the 30 days of Pb exposure, without being able to control it. We concluded that the increase of liver glycogen concentration was due to gluconeogenesis via lactate and lipolysis. Further experimentation on key gluconeogenic and lipolytic enzymes over the 30 days of Pb exposure would elucidate the mechanisms that may lead to such phenomena.

Nephrotoxic effects of lead nitrate in Rana ridibunda

“…This may be the reason for a well-known impairment of reabsorptive and secretory functions of proximal tubules (Herak-Kramberger and Sabolic 2001), leading to protein loss via urine. In an earlier study (Vogiatzis and Loumbourdis 2001) we recorded, in the very same animals, a continuous decrease of proteins from the liver. In that study we implicated possible kidney malfunction as a reason of this protein loss.…”

“…Most of lead's toxicity is ascribed to its action on proteins, where it binds to sulphydryl groups. As a result, many enzymes have reduced activity in the presence of lead (Vogiatzis and Loumbourdis 2001). As in mammals (Lock and Ishmael 1998;Mitsumori et al 1998;Leussink et al 2000) and fishes (Reimschuessel et al 1993), the first part of kidney damaged by xenobiotics and heavy metals is that of the PCT.…”

“…Rana ridibunda is a water frog widely distributed in Europe including Greece, and is a good bioindicator species, since it meets all the criteria of such a species (Lower and Kendal 1990). Some years ago we started a wide-ranging project studying the impact of heavy metals on this species, including kinetic (Loumbourdis et al 1999;Vogiatzis and Loumbourdis 1998, 1999a, 1999b and biochemical (Vogiatzis and Loumbourdis 2001) studies. In a series of experiments, we exposed the animals to 14 ppm Pb as Pb(NO 3 ) 2 for periods of 4, 10 or 30 days.…”

Assessment of Lead Ecotoxicity in Water using the Amphibian Larvae (Xenopus laevis) and Preliminary Study of its Immobilization in Meat and Bone Meal Combustion Residues

“…It has been employed in the past to manufacture of drain pipes, cookery pots, weapons and machinery (Vogiatzis & Loumbourdis 2001). More recently, it has been employed in many varieties of industrial applications and products such as storage batteries, chemicals, pigments, paints, gasoline (Moore & Ramamoorthy 1984;Landrigan 1990), in mining and smelting activities, and has been spread on agricultural land for instance in sewage sludge (Vogiatzis & Loumbourdis 2001).…”

Efeitos da poluição industrial sobre anuros (Amphibia) da Mata Atlântica

“…Em anfíbios, como nos demais vertebrados, o fígado tem como principal função a detoxificação do organismo, sendo um dos órgãos mais afetados pela presença de compostos químicos no ambiente (Vogiatzis & Loumbourdis 2001;Williams & Iatropoulos 2002). O fígado de um indivíduo exposto à contaminação sofre excesso de trabalho de detoxificação e pode apresentar aumento no número ou tamanho das células, alterações no metabolismo celular, acúmulo de poluentes, desenvolvimento de fibroses e granulomas (Williams & Iatropoulos 2002;Linzey et al 2003;Boncompagni et al 2004;Păunescu et al 2010 …”