Assessment of nociceptin/orphanin FQ and micro-opioid receptor mRNA in the human right atrium.
BACKGROUND
The expression of micro (mu: MOP) and nociceptin/orphanin FQ (NOP) receptors in the human myocardium is controversial. In this polymerase chain reaction (PCR)-based study using human right atrial biopsies, we have (i) probed for mRNA encoding NOP receptor and its endogenous peptide precursor, ppN/OFQ, and mRNA encoding MOP and (ii) attempted to correlate expression with cardiac function.


METHODS
mRNA encoding MOP, NOP, and the precursor for NOP (ppN/OFQ) was assessed by quantitative real-time PCR (Q-PCR) using validated TaqMan primers and compared with a housekeeper (glyceraldehyde-3-phosphate dehydrogenase, GAPDH). Q-PCR data are expressed as the difference in cycle threshold (DeltaC(t)=C(tGene of interest)-C(tGAPDH): high value, low expression) and patients were grouped according to left ventricular ejection fraction (LVEF).


RESULTS
Forty patients were recruited; NOP, MOP, and ppN/OFQ mRNA were measured in 38, 29, and 10 patients, respectively. DeltaC(t) (median and range) values for NOP and MOP were 10.9 (7.8-13.7) and 16.0 (12.3-18.9), respectively, representing low expression of MOP and approximately 34-fold more NOP. MOP mRNA was not detected in seven samples and with DeltaC(t) values of approximately 20, ppN/OFQ was considered absent. When patients were grouped into normal (>50%) and impaired (<50%) LVEF, there was no difference between the groups for either NOP or MOP. In some patients, intraoperative LVEF was estimated using transoesophageal echocardiography, and there was no correlation with either NOP or MOP.


CONCLUSIONS
The human right atrium of patients with coronary artery disease and heart failure expresses mRNA encoding NOP and possibly low levels of MOP. This does not correlate with degree of cardiac dysfunction. In addition, the atrium does not express ppN/OFQ mRNA.
McDonald
J
J
Department of Cardiovascular Sciences (Pharmacology and Therapeutics Group), Division of Anaesthesia, Critical Care and Pain Management, University of Leicester, Leicester Royal Infirmary, Leicester, UK.
Leonard
A D
AD
Serrano-Gomez
A
A
Young
S P
SP
Swanevelder
J
J
Thompson
J P
JP
Lambert
D G
DG
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001026:Coronary Artery Bypass; D003324:Coronary Artery Disease / Q000378:metabolism* / Q000601:surgery; D005260:Female; D006325:Heart Atria / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism*; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000235:genetics; D011957:Receptors, Opioid / Q000096:biosynthesis* / Q000235:genetics; D017450:Receptors, Opioid, mu / Q000096:biosynthesis* / Q000235:genetics; D013318:Stroke Volume / Q000502:physiology; D018487:Ventricular Dysfunction, Left / Q000378:metabolism; D016277:Ventricular Function, Left / Q000502:physiology; D000094942:Nociceptin Receptor
D012333:RNA, Messenger; D011957:Receptors, Opioid; D017450:Receptors, Opioid, mu; D000094942:Nociceptin Receptor; C000722283:OPRL1 protein, human