Dilatatory capacity of the coronary system in the anesthetized rat.

The minimal coronary vascular resistance was measured in anesthetized rats. For determination of coronary flow a tube system was inserted which directed the blood from the left carotid artery via the right carotid artery into the ostium of the left or the right coronary artery. A drop chamber in the shunt system enabled flow measurement. Maximal vasodilatation was induced by intra-arterial infusion of adenosine. In non-thoracotomized rats vascular resistance decreased to 20.6% and 20.3% of control values in the left and right coronary artery, respectively (23.8 to 4.9 18.2 to 3.7 mmHg X ml-1 X min X g). Thoracotomy led to increased control values (29.3 mmHg X ml-1 X min X g, right coronary artery). Minimal resistance in this latter group was nearly as low as in the closed-chest rats (4.8 mmHg X ml-1 X min X g). It can be assumed that the coronary dilator reserve in the rat lies within the same range as that of larger species e.g. dogs.