Comparison of Heavy Labeled (SIL) Peptide versus SILAC Protein Internal Standards for LC-MS/MS Quantification of Hepatic Drug Transporters

Table 4

Comparison of precision of protein quantification using SIL versus SILAC internal standard methods.

Transporter	Mean of standard deviation		Range of standard deviation for the 20 liver samples		𝑃 value; (paired 𝑡-test)
	SIL	SILAC	SIL	SILAC
OATP1B1	0.16	0.36	2.3–16.0	3.0–37.6	<0.001*
OATP1B3	0.10	0.25	2.2–27.2	8.2–90.3	0.03*
OATP2B1	0.10	0.10	1.1–14.0	1.2–9.2	0.53
P-gp	0.05	0.07	3.1–21.3	8.0–60.4	0.01*

∗The standard deviation of the individual log protein concentrations in each liver sample, estimated using the SIL or the SILAC internal standard method, was compared using the paired 𝑡-test. 𝑃<0.05 was considered significant.