Identification and quantification of 2',3'-cAMP release by the kidney.
We recently developed a sensitive assay for 3',5'-cAMP using high-performance liquid chromatography-tandem mass spectrometry. Using this assay, we investigated the release of 3',5'-cAMP from isolated, perfused rat kidneys. To our surprise, we observed a dominant chromatographic peak that was because of an endogenous substance that had the same parent ion as 3',5'-cAMP and that fragmented to the same daughter ion (adenine) as 3',5'-cAMP. However, the retention time of this unknown was approximately 2.9 min, compared with 6.3 min for authentic 3',5'-cAMP. We hypothesized that the unknown substance was an isomer of 3',5'-cAMP. The unknown substance had the same retention time and mass spectral properties as authentic 2',3'-cAMP. Renal venous secretion of 2',3'-cAMP was greater in kidneys from 20-week-old genetically hypertensive rats compared with age-matched normotensive rats (12.49 +/- 2.14 versus 5.32 +/- 1.97 ng/min/g kidney weight, respectively; n = 18). Isoproterenol (1 microM; beta-adrenoceptor agonist) increased renal venous 3',5'-cAMP secretion (approximately 690% of control) but had no effect on 2',3'-cAMP production. In contrast, rapamycin (0.2 microM; activator of mRNA turnover) and iodoacetate + 2,4-dinitrophenol (50 microM; metabolic inhibitors) increased the renal venous secretion of 2',3'-cAMP (approximately 1000 and 4100% of control, respectively) while simultaneously decreasing the renal venous secretion of 3',5'-cAMP. In conclusion, 2',3'-cAMP is a naturally occurring isomer of 3',5'-cAMP that is: 1) not made by adenylyl cyclase; 2) released from kidneys into the extracellular compartment; 3) released more by kidneys from rats with long-standing hypertension; 4) derived from mRNA turnover; and 5) increased by energy depletion.
Ren
Jin
J
Department of Medicine, Center for Clinical Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
Mi
Zaichuan
Z
Stewart
Nicolas A
NA
Jackson
Edwin K
EK
D000227:Adenine Nucleotides / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D000242:Cyclic AMP / Q000032:analysis; D006973:Hypertension / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D008297:Male; D013058:Mass Spectrometry; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D000227:Adenine Nucleotides; C010565:2',3'-cyclic AMP; D000242:Cyclic AMP