Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:In view of the lack of effect of 3 days of UUO on AT1 and AT2 receptor mRNA in either obstructed or contralateral kidneys (48), it is likely that these effects are mediated by signaling downstream from ANG binding with its receptors and modulated by the stretched tubules in the obstructed kidney.
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