Salivary gland K+ transport: in vivo studies with K+-specific microelectrodes

Stimulation-induced transport of K+ in the submandibular salivary gland of cats and dogs anesthetized with pentobarbital was studied with an extracellular K+-specific microelectrode. Electrical stimulation of the para-sympathetic chorda-lingual nerve caused a rapid transient increase in extracellular K+ concentration from 2.2 to 18.7 meq/liter in the cat and from 2.3 to 15.2 meq/liter in the dog. Eventually the K+ concentration fell below the prestimulatory level, indicating uptake of K+ by the gland cells. In case of prolonged stimulation (2-10 min), the uptake began during stimulation. However, a further reduction in extracellular K+ concentration occurred upon cessation of stimulation, a result that demonstrated that the cells did not fully recover their K+ ,content during stimulation. The latency of the release of K+, defined as the time from the beginning of stimulation to the point at which, the K+-specific microelectrode signal had increased by 2 mV, was 0.6 s in the cat and 0.8 s in the dog. Because these are overestimates of the "true" latencies, we conclude that the K+ release begins simultaneously with the hyperpolarization of the acinar cell membrane.