Validation of transit-time flowmetry for chronic measurements of regional blood flow in resting and exercising rats

Abstract

The objective of the present study was to validate the transit-time technique for long-term measurements of iliac and renal blood flow in rats. Flow measured with ultrasonic probes was confirmed ex vivo using excised arteries perfused at varying flow rates. An implanted 1-mm probe reproduced with accuracy different patterns of flow relative to pressure in freely moving rats and accurately quantitated the resting iliac flow value (on average 10.43 ± 0.99 ml/min or 2.78 ± 0.3 ml min -1 100 g body weight -1 ). The measurements were stable over an experimental period of one week but were affected by probe size (resting flows were underestimated by 57% with a 2-mm probe when compared with a 1-mm probe) and by anesthesia (in the same rats, iliac flow was reduced by 50-60% when compared to the conscious state). Instantaneous changes of iliac and renal flow during exercise and recovery were accurately measured by the transit-time technique. Iliac flow increased instantaneously at the beginning of mild exercise (from 12.03 ± 1.06 to 25.55 ± 3.89 ml/min at 15 s) and showed a smaller increase when exercise intensity increased further, reaching a plateau of 38.43 ± 1.92 ml/min at the 4th min of moderate exercise intensity. In contrast, exercise-induced reduction of renal flow was smaller and slower, with 18% and 25% decreases at mild and moderate exercise intensities. Our data indicate that transit-time flowmetry is a reliable method for long-term and continuous measurements of regional blood flow at rest and can be used to quantitate the dynamic flow changes that characterize exercise and recovery.

Effect of gender on training-induced vascular remodeling in SHR

“…The redistribution of cardiac output is responsible for maintaining an adequate perfusion to exercised skeletal muscles in which the metabolic needs are enormously increased. Measuring hind limb flow by the transit-time ultrasonic technique in rats at rest and during an acute bout of exercise we were able to reproduce this phenomenon (53). Figure 4 illustrates that at the beginning of exercise (even at mild exercise of 0.4 km/h) there was a large and prompt increase in hind limb blood flow (vasodilatation of the iliac artery) that attained a steady-state plateau between the 1st and 2nd min of exercise.…”

Continuous flow phantom for the calibration of an ultrasonic transit-time flowmeter

“…No papers regarding a TTFM flow phantom designed with silicone tubes in the measurement regions were found. Water has been the most cited fluid (Bednarik and May, 1995;Drost, 1978;Gordon, 1995), except for cases in which salt solutions were employed in ex vivo veins and arteries (Amaral and Michelini, 1997;Beldi et al, 2000;Groom et al, 2001;Lundell et al, 1993). The use of hydrostatic pressure for pressurization was found in the Transonic System calibration manual (Transonic…, 2009).…”

“…The materials employed in the measurement region ranged from synthetic materials, such as latex (Drost, 1978;Transonic…, 2009) and dialysis tubing (Bednarik and May, 1995;Gordon, 1995), to biological materials, such as saphenous human vein grafts (Beldi et al, 2000;Groom et al, 2001), carotid arteries of rats (Amaral and Michelini, 1997), sheep (Lundell et al, 1993) and pigs (Beldi et al, 2000). Water is the working fluid that is normally employed, but there are also reports of the use of saline solution in experiments with biological materials (Beldi et al, 2000;Groom et al, 2001).…”

“…Known methods do not have a common experimental protocol and incur a high implementation cost (Amaral and Michelini, 1997;Bednarik and May, 1995;Beldi et al, 2000;Gordon, 1995;Groom et al, 2001;Lundell et al, 1993;Transonic…, 2009), which indicates the importance of establishing a well-defined method for TTFM calibration that is inexpensive and has an easy acquisition phantom.…”

Is Gender Crucial for Cardiovascular Adjustments Induced by Exercise Training in Female Spontaneously Hypertensive Rats?

“…11,18,20 Heart dynamics during the cardiac cycle (left ventricle [LV] systolic pressure and LV diastolic pressure, positive dP/dt max and negative dP/dt max ) were measured in other groups of anesthetized rats (ketamine/xylazine/acepromazine, 0.7/0.2/0.1 vol/ vol/vol; 0.04 mL/kg, IM) with a catheter placed into the LV through the right carotid artery. AP and HR were also measured during anesthesia, after replacing the arterial catheter into the carotid artery.…”