On the function of myoepithelial cells in salivary glands

Abstract

1. In dogs under chloralose-urethane anaesthesia the submaxillary duct was cannulated and connected either to an open outflow system, in which saliva displaced water, or to a closed pressure recording system.2. The secretory cells, which are supplied with beta-adrenoreceptors, were stimulated with isoprenaline, adrenaline or sympathetic nerve stimulation. Myoepithelial cells, supplied with alpha-receptors, were activated with phenylephrine, adrenaline or sympathetic stimulation, and also with bradykinin. To abolish alpha-receptor stimulating effects of adrenaline and sympathetic nerve stimulation, dihydroergotamine, phenoxybenzamine and phentolamine were used.3. When the secretory cells were activated alone, saliva flowed from the salivary duct, but the flow started late and only a moderately high pressure could be produced in the closed system. Saliva appeared much earlier in the duct when secretion was combined with myoepithelial contraction, and a much higher pressure could be built up in the duct system.4. It is concluded that rapid emptying of saliva in the mouth and a maintained flow at a high rate of the viscous saliva is promoted by contractions of the myoepithelial cells.