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Journal of Experimental Biology 58,549-564 (1973)
Published by Company of Biologists 1973

Ion and Water Balance in the Ixodid Tick Dermacentor Andersoni : III. Influence of Monovalent Ions and Osmotic Pressure on Salivary Secretion

W. R. KAUFMAN ¹ and J. E. PHILLIPS ²

¹ Department of Zoology, University of British Columbia, Vancouver 8, Canada; School of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 OES England
² Department of Zoology, University of British Columbia, Vancouver 8, Canada

1. The salivary gland of the ixodid tick, Dermacentor andersoni, can be induced to secrete fluid for at least 6 h when bathed in an artificial medium in vitro.

2. Fluid secretion appears to be a consequence of active Cl secretion since (a) it is inhibited by 95% when nitrate and by 100% when acetate replaces Cl in the bathing medium; however, bromide can support secretion as well as Cl, (b) the rates of fluid and Cl secretion are linearly related to the concentration of Cl in the medium; and (c) the S/H ratio for Cl is greater than unity at all concentrations despite a transacinar P.D. of 35 mV (lumen negative).

3. Although (in the presence of Na) a low concentration of K in the bathing medium stimulates the rate of fluid secretion fivefold, higher concentrations of K inhibit fluid secretion. The latter is largely due to a direct effect of K ion and not simply to increased osmotic pressure or reduced Na concentration. Fluid secretion is completely in hibited by 10^-6 M ouabain. On the basis of these observations we propose that fluid secretion may be dependent on a Na-K activated ‘pump ATPase’, which is somehow involved in cation secretion. The S/H ratios of Na and K are greater than unity at all medium concentrations.

4. The saliva secreted in vitro is slightly hypo-osmotic to the bathing medium over a wide range of medium concentration (300-920 mOsm/l). We postulate that the primary saliva is iso- or hyper-osmotic to the bathing medium; the final elaborated saliva is probably rendered hypo-osmotic by a process of solute reabsorption somewhere between the acini and the orifice of the main salivary duct.