LC-MS/MS SRM chromatogram of renal venous perfusate obtained from
untreated, isolated, and perfused SHR kidney. Two transitions were monitored:
278 → 141 m/z for the internal standard (top), which
was 13C10-adenosine; and 330 → 136
m/z for endogenous 3′,5′-cAMP (bottom). Note the
prominent peak with a retention time of approximately 2.9 min (bottom), which
was much too short to be 3′,5′-cAMP, which has a retention time of
approximately 6.3 min.