Summary. Studies on the electrolyte compositioii of the adnar (or primary) secretion and the final saliva of the cat submaxillary gland untlerfjoing parasympatho-and sympathomimetic stimulation have been undertaken using uiicropuncture and duct cannulation techniques for sample collection. The work was undertaken to see to what extent the two-stage secretory model developed previously for rat salivary glands would hold for rather different glands of other species. We find that in genera! tenns the .same two-stage model is apphcable. The primary secretion in both species has plasma-like .sodium and chloride concentrations and potassium concentrations about twice those of plasma; gland stimulation does not greatly alter the composition of this fluid. In the secondary stage, during passage of this fluid altnig the gland excurrent ducts, there is. in both species, extensive ductai absorption of sodium and chloride, although for the cat the absorptive mechanism is more easily saturable. Unlike rat submaxillary ducts, however, those of the cat appear to secrete little potassium. and gland stimulation does not increase the secretory rate of this ion. so that the phenomenon termed acino-tubular balance is not observed. Although both ducts may secrete bicarbonate this is much more conspicuous for the rat. In contrast to parasympathomimetic stimulation, the effects of sympathomimetic stimulation on the two glands were totally different, In the cat a much more vigorous secretorj' response was obtained than in the rat but the striking elevation of salivar>' potassium and bicarbonate concentrations to values in excess of 100 niM seen in the rat did not occur. It Ls concluded that while a two-stage hypothesis may account for secretion of water and electrolytes in many salivary glands, the role of ductai stimulation in the secondary stage and the relative roles of sympathetic and parasympathetic stimulation may vary greatly among species.
INTRODUGTION.The adaptation of renal micropuncture techniques to the study of electrolyte transport in .salivan' glands (Martinez, Holzgreve and Frick, 1966;Young and Schogel, 1966) has tlu^own a great deal of light on their secretory mechanisms. For reasons of convenience these micropuncture experiments were carried out 68on the salivary glands of only one species, the rat, although it was soon realized that most rat exocrlne secretions are rather atypical in ha\'ing extremely high potas.sium concentrations. This holds not only for the three major salivary glands, the submaxillary (Young and Schogel, 1966), the sublingual (Martin and Young, 1971a) and the parotid (Mangos and McSherry, 1969), but also for rat sweat glands (Brusilow, Ikai and Gordes, 196S) and lacrinial glands (Alexander, van Lennep and Young, 1972) as well as for the pancreas (Sewell and Young, unpublished observations). It seemed highly desirable to extend our .studies to include a hypotonicsecreting salivary gland from another species in which salivary potassium concentrations were more typical of exocrine glands in ge...