In six open-thorax-anaesthetized dogs with paced hearts and a retrogradely cannulated epicardial lymph vessel, the sensitivity of myocardial lymph pres- sure to left ventricular pressure during systole and during diastole was determined. The lymph vessels were can- nulated using PE-90 tubing, and lymph pressure was measured by connecting the cannula to a microtip press- ure transducer. To obtain the systolic sensitivity, left ven- tricular pressure was changed by clamping the de- scending aorta, which caused left ventricular pressure to increase. The diastolic sensitivity was obtained from natural variation to left ventricular pressure caused by atrial contractions during induced long diastoles. The mean ratio of the pulse in lymph pressure to the pulse in left ventricular pressure was determined: systole: 0.069 + 0.013, n = 213, diastole: 0.76 -+ 0.16, n = 249 and, if possible, linear regression analysis between lymph and left ventricular pressure was performed. The systolic regression coefficients could be determined in six dogs and the diastolic coefficients in three dogs. Dur- ing long diastoles lymph pressure variations are on aver- age 76 per cent of those in the left ventricle. However, during systole, the sensitivity of lymph pressure to left ventricular pressure is more than ten times lower. It is not unlikely that the structural embedment of lymph ves- sels within the myocardium is such that volume vari- ations by cardiac contraction are limited. @en

he rate of change of coronary adjustment in the anesthetized dog to a step change in heart rate (HR) and in perfusion was analyzed. The left main coronary artery was perfused either at constant pressure (CP) or at constant flow (CF). Coronary arterial pressure and flow were continuously measured and averaged per beat, after which their ratio, being an index of coronary resistance in steady state, was calculated. The rate of change of pressure-to-flow ratio was quantified by t50, the time required to establish half of the completed response. The t50 values for the dilating responses at CP were 5.5 +/- 0.4 (SE) s for an increase in HR and 5.5 +/- 0.1 s for a decrease in perfusion. At CF these values were 9.3 +/- 0.9 and 9.7 +/- 1.6 s, respectively. The t50 values for the constricting responses with CP were 6.6 +/- 0.5 s for a decrease in HR and 6.2 +/- 0.2 s for an increase in perfusion. At CF these values were 12.2 +/- 1.5 and 10.8 +/- 2.2 s. The responses in the dog are faster than in the goat. Furthermore, the directional sensitivity in responses with perfusion changes, observed earlier in goats, is normally absent in dogs. @en