Aspects of lymph-heart function inRana catesbeiana

Abstract

The effect of voluntary dives on the posterior lymph heart rate of the bullfrog, Rana catesbeiana, was tested and compared with the blood-heart rate (n = 6). This was performed by cannulating the posterior lymph heart and femoral artery simultaneously. Blood-heart rates during submergence were significantly lower (α = 0.05) then pre-submergence rates at all sampling times. In contrast, the lymph hearts showed significantly lower rates only during the first and last submergence intervals. It is believed that the lymph-heart bradycardia found during these intervals is due in part to the physiological "preparations" for diving by the frog. Further information regarding posterior lymph heart contractions was gained by cannulating two posterior lymph hearts on one side of the frog (n = 5). It was found that these hearts beat within 100 ms of each other between 66 and 97% of the time (α = 0.05). The combined contraction of the three posterior lymph hearts could facilitate the movement of lymph through the outflow valve and into the venous circulation. This study represents the first time the axial coordination of homolateral lymph hearts has been shown to extend to the multiple posterior lymph hearts.