Table 2.

Histopathologic Analysis of Kidneys from WT and Mrp2-Null Mice after Cisplatin Injection

Mice and time after injection	Histopathologic grade						Mice with grade ≥2 (%)
	0	1	2	3	4	5
WT
Control	13	0	0	0	0	0	0
2 Days	1	6	0	0	0	0	0∗
3 Days	1	2	2	0	0	0	40∗
4 Days	4	3	6	1	0	0	50∗
Mrp2-null
Control	13	0	0	0	0	0	0
2 Days	1	4	2	0	0	0	29∗
3 Days	1	1	3	0	0	0	60∗
4 Days	0	1	3	6	2	0	91∗†

Kidneys were removed 2 to 4 days after 20 mg/kg of i.p. cisplatin or vehicle injection and were fixed in zinc formalin before paraffin embedding and staining with H&E. Kidney slices were evaluated for the severity of degeneration and necrosis in proximal tubule segments. Histopathologic scoring of renal proximal tubule degeneration and necrosis by a veterinary pathologist was as follows: grade 0, no injury; grade 1, minimal injury involving <10% of cells with degeneration or necrosis; grade 2, mild injury involving 10% to 25% of cells; grade 3, moderate injury involving >25% to 40% of cells; grade 4, marked injury involving >40% to 50% of cells; grade 5, severe injury involving >50% of cells. The number of mice with a particular histopathologic grade is shown in each column. Mice with grades ≥2 are considered to have significant kidney injury. The ratios of mice with grades ≥2 compared with the total number of mice are presented as percentages. Histopathologic grades were rank ordered before statistical analysis.

^∗P < 0.05 compared with genotype control mice.

^†P < 0.05 compared with cisplatin-treated WT mice.