EFFECTS OF COLLAGENASE, ELASTASE, AND HYALURONIDASE ON MECHANICAL-PROPERTIES OF ISOLATED DOG JUGULAR VEINS

To study the contribution of tissue components to the mechanical prope rties of veins, pressure-volume relationships were obtained with the c ylindrical segments of isolated dog external jugular veins at several levels of longitudinal extension. At each length, the transmural press ure of the segment was raised up to 20 cmH2O and then reduced to 0 cmH 2O by increasing and decreasing the intraluminal volume at a constant rate. The longitudinal extension of the venous segments caused a signi ficant reduction in the incremental volume elasticity within the press ure range of 0-2 cmH2O (E0-2) as well as a significant increase of the incremental volume elasticity within 10-20 cmH2O (E10-20). The pressu re-volume relationships of venous segments were also constructed in th e same way after treatment with 1 mg/ml collagenase for 30 min, 0.1 mg /ml elastase for 5 min, or 1 mg/ml hyaluronidase for 60 min. Treatment with collagenase or elastase produced a significant increase of the E 0-2. The treatment, however, caused no effect on E10-20. Treatment wit h hyaluronidase induced no effect on these mechanical parameters but p roduced a significant attenuation of the extension-induced decrease in E0-2. Activation of the venous smooth muscles induced by norepinephri ne (10(-4) M) or high-potassium Krebs solution caused a significant de crease of E0-2 as well as a significant increase of E10-20. A complete relaxation of the smooth muscles elicited by Ca2+-free Krebs solution containing ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetra acetic acid (2 mM) caused an increase of E0-2. Mechanical rubbing of t he endothelium caused no significant effect on E0-2 and E10-20. These results suggest that both the mechanical properties of noncontractile fibers connected with smooth muscle cells in the walls and the myogeni c activity of the cells may contribute to the venous distensibility ov er the physiological range of transmural pressure and that the contrib ution of the endothelium to the venous distensibility is hardly observ ed.