Biomechanical model for the myogenic response in the microcirculation: Part II--Experimental evaluation in rat...

In order to test experimentally a novel model for myogenic contraction of the arterioles, presented in Part I of this series, a sequence of in-vivo studies was performed on arterioles of rat cremaster muscle using a modified "Box Method." The tissue was enclosed in a sealed chamber in which the extravascular pressure could be changed as a means of stimulating the myogenic response. The microvascular pressures were measured using an improved cremaster preparation with intact distal feeder. The experiment consists of measurements of a static myogenic response and the response to a step extravascular pressure, as well as passive viscoelastic properties of the arteriole. These measurements served to determine the parameters involved in the theoretical model. The model prediction were then compared with in-vivo observations during a ramp and during oscillatory extravascular pressure changes in the same arterioles. The results indicate that the model is capable of quantitatively predicting time dependent in-vivo changes in response to transmural pressure. The measured model parameters suggest an increase in myogenic activity from proximal arcade arterioles to more distal transverse arterioles in cremaster muscle of Wistar rats.