Circulatory effects on osmotic water exchange in Rana pipiens

Tritiated water (3H2O) exchange was shown to be more sensitive to circulatory changes than to arginine vasopressin (ADH)-induced permeability changes. Reducing the circulation (sciatic artery ligation) and increasing the circulation (severing the sciatic nerve) caused the 3H2O exchange in frog legs to decrease from 6.0 +/- 1.3 (5) to 3.5 +/- 0.5 and increase from 6.0 +/- 0.7 (10) to 8.6 +/- 0.6 ml.h-1, respectively. In contrast injection of ADH caused a negligible increase in 3H2O exchange from whole frogs, while at the same time causing a significant increase in osmotic water exchange from 0.22 +/- 0.08 (6) to 0.63 +/- 0.13 (6) g.100 cm-2.h-1.200 mosM-1. Circulatory changes in whole frogs were produced by inducing a diving bradycardia that was less pronounced in a bath aerated with oxygen than with air. The bradycardia caused a reduction in skin circulation, as measured by 3H2O exchange, from 0.210 +/- 0.007 (16) to 0.17 +/- 0.006 (16) ml.h-1.cm-2 in air mixed media and from 0.149 +/- 0.009 (16) to 0.135 +/- 0.011 (16) in oxygen mixed media. Diving bradycardia was also found to affect osmotic water uptake which decreased from 0.61 +/- 0.05 (16) to 0.39 +/- 0.03 (16) g.100 cm-2.h-1.200 mosM-1 in air mixed media and from 0.61 +/- 0.05 (16) to 0.51 +/- 0.04 (16) in oxygen mixed media. The results indicate that circulation affects osmotic water exchange.