Depends how many samples do you have? If you have 30 samples from 30 rats then you need 60 wells (30 x 2 - duplicates) plus your standards around 7 + 1 Blank (around 16 wells - as duplicates) ... which in total would be 76 wells.
Hello, 96 wells plate enough as described above. If you have separation by groups which mean same experiment done in group, you can a little bit reduce the number by taking duplicates not from all samples just half from group samples.