The relationship between [K+] in venous effluent blood and alterations in mean arterial blood pressure was studied during static handgrip contractions at 15 and 30% of maximal voluntary contraction (MVC). 2. To further elucidate the importance of K+ in the reflex regulation of blood pressure a situation with normal recovery was compared with a situation in which 3 min of post-exercise occlusion was applied by arresting the circulation to the forearm just prior to the cessation of the contraction. 3. There was a temporal as well as quantitative correlation between venous [K+] and the blood pressure response during and after static exercise. During 30% MVC mean arterial blood pressure (MAP) attained 161.7 mmHg and venous [K+] 5.8 mM, while the corresponding values during 15% MVC were 121.5 mmHg and 5.0 mM. 4. In the occlusion period mean arterial blood pressure remained elevated above resting level and provided a measure of the magnitude of muscle chemoreflexes. In the same period venous [K+] was maintained at 5.3 mM and 4.6 mM following 30% MVC and 15% MVC respectively. This is indicative of interstitial concentrations of above 8-10 mM. This level is sufficiently high to stimulate type III and IV muscle afferents involved in the reflex regulation of blood pressure, and strengthens the notion that K+ may play an important role in eliciting the pressor reflex. 5. In contrast to [K+] the time course of venous blood concentrations of lactate and ammonia (NH3) exhibited a clear dissociation from the blood pressure recordings.
