Cardiac microdialysis to estimate interstitial adenosine and coronary blood flow

Abstract

The purpose of this study was twofold: 1) to investigate the feasibility and usefulness of cardiac microdialysis for the simultaneous estimation of regional cardiac interstitial fluid (ISF) adenosine (ADO) concentration and coronary blood flow (CBF); and 2) to determine the changes in the ISF levels of ADO and CBF during cardiac stimulation or regional myocardial ischemia. Cardiac microdialysis probes were implanted in the left ventricular myocardium of chloralose-urethan-anesthetized dogs and perfused with Krebs-Henseleit buffer. The concentration of ADO in the effluent dialysate was used as an index of intramyocardial ISF ADO concentration while local CBF was measured by H2 clearance via a platinum wire within the dialysis fiber. Dialysate ADO was elevated immediately after insertion of the microdialysis probe, declined rapidly in the first 20 min, stabilized by 60 min, and remained constant for 2 h. Based on the relationship in vitro and in vivo between microdialysis probe perfusion rate and dialysate ADO concentration, ISF ADO concentration within the left ventricular myocardium was estimated to be 0.9-1.3 microM. Dobutamine (10 micrograms.kg-1.min-1) infusion resulted in a 36% increase in CBF and a 2.5-fold increase in dialysate ADO (n = 9; P less than 0.05). Regional myocardial ischemia, induced by occlusion of the left anterior descending artery (LAD), caused a 13-fold increase in dialysate ADO in the LAD perfused myocardium (n = 9; P less than 0.05). These results are consistent with the ADO hypothesis and suggest that cardiac microdialysis provides a reliable technique for the sampling of regional intramyocardial ISF.

Evidence for Angiotensin-Converting Enzyme– and Chymase-Mediated Angiotensin II Formation in the Interstitial Fluid Space of the Dog Heart In Vivo

“…This was addressed in the heart by Van Wylen and coworkers. 12 These investigators found that adenosine levels were elevated immediately after implantation but rapidly declined within the first 20 minutes after implantation. A rapid decline in ISF concentrations of adenosine and other compounds has also been reported after implantation of microdialysis probes in the brain, 28 suggesting that the initial effects of tissue damage dissipate rapidly.…”

“…The cardiac microdialysis technique is similar to that developed by Van Wylen and coworkers 12 and subsequently used in our laboratory. 11 Each microdialysis probe (Clirans, Terumo Corp) is a semipermeable-membrane probe with a molecular-weight cutoff of 35 kDa and an ID of 200 m, which is connected to methyl-deactivated silica capillary tubing (OD, 0.17 mm).…”

“…12 The dialysate concentration is therefore an estimate of intramyocardial ISF concentration. However, at the flow rates used in the microdialysis experiments in vivo, it is unlikely that complete equilibration occurs between the normal saline within the fiber and the cardiac ISF in the vicinity of the fiber.…”

“…Therefore, we performed in vitro experiments to estimate recovery from our microdialysis probes by the method described by Van Wylen and coworkers. 12 Assuming that all probes have the same area available for diffusion, the recovery (determined by comparing the concentration in the dialysis probe effluent with that of the medium, ie, the percent recovery) depends primarily on the perfusion rate through the dialysis fiber. A recovery of 17% was used in the final calculation of ISF values, as validated by in vitro experiments previously performed in our laboratory.…”

Interstitial Accumulation of Na+ and K+ During Flush–Out and Cold Storage of Rat Livers: Implications for Graft Survival

“…Microdialysis tubes were designed as described by Wylen et al 14 Single dialysis fibers were removed from a cellulose hemodialysis filter (Terumo Clirans TH 10 cellulose, Terumo, Japan; outer diameter: 200 µm), and hollow silica tubing (outer diameter: 140 µm; 10VS, Scientific Glass Engineering, Weiterstadt, Germany) was glued into the dialysis fiber to obtain a sampling window of 1 cm. The inflow silica tube was connected via a larger silica tube (outer diameter: 300 µm; 25VS, Scientific Glass Engineering) to a gas-tight glass syringe, filled with Krebs-Henseleit buffer (KHB) (140 mmol/L NaCl, 4.7 mmol/L KCl, In Vitro Na ؉ and K ؉ Recovery.…”