Chapter-1 / Physiological Foundations - WHNLive Public Library

A100pmI IBFig. 104 Tip of a pH microelectrode before (A) and after (B) isolation with silicone rubber (free length of thesensitive tip is a few 100 /oLm)make possible the measurement and recordingof the pH values. Figure lOS shows this experimentin the stage before a small coronary vesselbranch on the ventral side of the left ventriclewas ligated. For the simulation of a coronarymyocardial infarction, the loop used for thispurpose could, after stabilization of the pHstarting level, be more or less tightly pulledtogether using two pairs of tweezers andavoiding any further influence on the positionof the heart; the loop could also, if necessary,be loosened again at a desired moment, byinserting a fine needle between the thread andthe myocardium.Using the experimental set-up discussed (Fig.106) we could record the pH course in the O2deficient region of the myocardium of rats inthe course of an experimentally generated infarction.In all experiments there occurred avery ub tantial drop in the pH immediatelyf er the triggering of the 02 deficiency in theyocardium, a a re ult of a local incr~a e ,inic acid concentration. It can be seen In Ig.6 how the P02 ill the supply ar a of the r I •ve el ink by ApH = 1 within 2 min.immediately after the constriction of a coronaryvessel branch of the left ventri Ie. A aresult of the incomplete ligature and a remainingsupply from other sources (collateral ve ­sels, diffusion from the environment) thereoccurs a pH level of 6.2. The remaining upplycan be proven by the fact that when artifi ialrespiration of the animal i topped the pH immediatelydrops further and then reache a Ie elof 5.2 within 16 min. This al 0 how how f tand how low the pH in the myocardium mu tdrop and cause damage to the ti ue (mi rocirculationinhibition, va cular ·poro it increasein red cell aggregation relea and a ti a­tion of the Iy osomal enzyme tol ti hainreaction etc.) when, a can be e pe ted in lar rhearts (in humans for example) th inf r tmechani m proceeds in u h a wa that th r ino remaining upply from th nvir nm nt.The method of pH r gi tratitemporarily brought und r 2w 11 uit d to giv inf rm ti nth damag au d b n dand dur ti n f th impairm nt