The Mechanism of Establishment of Secretory Potentials in Sublingual tiland Cells.

Abstract

Summary.An attempt has been made to analyse the mechanism of establishment of the secretory potential over the outer gland cell membrane in the sublingual gland of the cat, as well as its importance for the secretion of salt and water.Double‐barrelled microelectrodes were inserted into gland cells permitting recording of the intracellular potential with current flow through one channel to change the membrane potential. The secretory potential over the outer membrane could still be evoked when the membrane potential had been raised to more than 100 mV. It is concluded that this secretory potential is due to an active transport of ions over the outer membrane and assumed to be an inward transport of anions.The resistance between the cell interior and the external medium measured with this technique was about 2 Mω in the resting state and 1.8 Mω during activation. Measurement has also been made of the resistance between the external medium and the lumen of the gland cell tubule and of the ratio of the resistances offered by the inner and outer gland cell membranes to a current passed between the external medium and the lumen. On the basis of these measurements and the assumption that the gland cell tubule can be considered as a core conductor the specific resistances of the outer and inner gland cell membrane were derived to 18 respectively 11 ohm cm2 in the resting cell. With activation there was no significant change in the resistance of the inner cell membrane, whereas the resistance of the outer membrane decreased by about 50 per cent.The anionic content of the saliva secreted by a number of gland cells with a certain area of outer membrane has been compared with the amount of current needed from an external battery to equal the secretory potential over this area of outer gland cell membrane. The probable order of magnitude of the active anionic transport is discussed in view of these findings.The hypothesis is forwarded that secretion of salt and water largely is caused by active transport of anions (mainly or exclusively chloride) over the outer gland cell membrane.