The effects of perfusion of the cutaneous vasculature on sodium uptake across isolated frog skin

Perfusion of cutaneous capillaries in isolated frog skin may remove an unstirred layer along the basolateral membrane of the epidermis that may affect the rate of cutaneous Na+ uptake. To test this hypothesis, the cutaneous artery and vein of a bullfrog were cannulated to allow perfusion of isolated flank skin while the rate of Na+ influx was determined. Rates of sodium influx with and without perfusion were determined in the same experiment. Na+ uptake increased by 59±4.8% during the 1st 0.5 h of perfusion relative to the control, pre-perfusion period and then remained at 26±5.3% above control values. Concomitant with the increase in sodium uptake, the transepithelial potential difference fell by ca. 10% within the 1st 0.5 h of perfusion. The amount of labeled sodium leaving the skin in the venous effluent decreased exponentially in the 1st 0.5 h of perfusion, suggesting a wash out of an unstirred layer within the interstitial fluid. Sodium in the venous outflow accounted for ca. 25% of the sodium uptake during each perfusion period. Perfusion of the cutaneous vasculature thus has a significant effect on Na+ transport and may potentially play a role in the acute regulation of cutaneous ion transport.