ANALYSES OF THE PH DEPENDENCE OF RESTING AND ACTIVE TENSIONS OF SOME TOAD BLOOD VESSELS

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Abstract
The mechanical characteristics of the toad blood vessels were investigated under different pHs using a dynamic strain amplifier. The resting tension of the vessels had 3 peaks at pH2, pH 5, and pHl2, and in the range pH3 to pHIO decrease slightly when the pH was altered in either direction from 7.4. Active tension was developed between pH3 and pHll, reaching a maximum level at pH 9. In solution made hypertonic by adding sucrose, the active tension and the peaks in the resting tension at pH5 and pH12 disappeared. Furthermore, the peaks in the resting tension at pH5 and pH 12 were irreversible. The peaks in the resting tension at pH 5 and pH 12 were due to acid and alkali contractures of the muscle component. Vessels, treated with crude trypsin, so that only the collagen component remained functional, showed acid contracture at pH2 and slight alkali contracture at pH12, supporting the conclusion that the peak in the resting tension of the vessels at pH2 was mainly due to the collagen component, and that at pH12 partly due to the collagen component. Vessels digested with formic acid, so that only the elastin component remained functional, showed an almost constant response at different pHs over a wide range, but when out of this range, the resting tension decreased, the decrease being more rapid on the alkaline side.