You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Nephroprotective effect of calcium channel blockers against toxicity of lead exposure in mice. Exposure to lead (Pb) can induce kidney damage, which is related to induction of oxidative damage and disturbance of intracellular calcium homeostasis. Pb can readily permeate through dihydropyridine-sensitive L-type calcium channels and accumulate within cells. The objective of this study was to investigate protective effects of calcium channel blockers (CCBs) verapamil and nimodipine on nephrotoxicity induced by Pb acetate in mice. One hundred and twenty male mice were randomly divided into 6 groups: control, Pb, low-dose verapamil, high-dose verapamil, low-dose nimodipine and high-dose nimodipine (n=20 per group). Pb acetate was injected intraperitoneally (i.p.) at 40 mg/kg body weight/day for 10 days to establish the Pb toxicity model. While control mice received saline, mice of the treated groups simultaneously received i.p. injections of verapamil or nimodipine daily for 10 days. Both verapamil and nimodipine showed protection against Pb-induced kidney injury, including alleviation of renal pathological damage and decreasing the level of Pb in kidney homogenate and extent of apoptosis in nephrocytes. Moreover, verapamil and nimodipine significantly down-regulated levels of blood urea nitrogen and creatinine in the serum. In addition, verapamil and nimodipine administration decreased malondialdehyde content and increased activities of super oxide dismutase activity and glutathione peroxidase in the kidney homogenate. The findings in the present study implicate the therapeutic potential of CCBs for Pb-induced nephrotoxicity, which were at least partly due to the decrease of Pb uptake and inhibition of lipid peroxidation.
{"Chemical": ["Pb", "glutathione", "super oxide", "verapamil", "calcium", "malondialdehyde", "creatinine", "urea", "nitrogen", "Pb acetate", "nimodipine"]}