The effect of deoxycorticosterone on the interstitial fluid pressure in normal rats.

Interstitial fluid pressure was measured by Guyton's capsular method in the subcutaneous tissue of rats after a single DOC i.p. injection. Regardless of the dose of DOC, the pressure-time curve showed three phases: latency, decrease and recovery. The maximum drop in pressure and the recovery time were dose-dependent. Maximum decrease in interstitial fluid pressure after 0.25; 0.50; 0.75; 1.00 mg/100 g body wt of DOC was 3.2; 7.1; 9.2 and 10.6 mmHg, respectively. It was found that the recorded pressure response is not exclusively caused by Starling forces. A correlation was found between the pressure decrease and the extracellular potassium loss. The role of potassium in the DOC-induced pressure response was verified by administration of the specific potassium ionophore, valinomycin. Due to the effect of valinomycin, potassium ion transport and, as a consequence, the interstitial pressure response, were accelerated.