title: Na+ influx mechanisms in submandibular salivary cells of newborn rats.
abstract: Uptake of this isotopic tracer was essentially the same as in cells derived from salivary glands of adult animals, both in the absence and in the presence of 1 microM acetylcholine, 10 microM monensin or 10 microM A23187. Tracer accumulation in resting cells was inhibited in the immature cells by 1 mM amiloride but the inhibition was significantly smaller than in fully mature cells (16 and 33%, respectively). Bumetanide inhibited tracer uptake by 28% in mature cells not exposed to agonist, but had essentially no effect in those of newborn rats. The tracer content of adult cells exposed to acetylcholine in Ca(2+)-free incubation solutions was significantly reduced when compared to that of cells exposed to agonist in solutions containing 1.0 mM CaCl2. A similar but significantly smaller reduction in tracer content was observed in cells of newborn animals incubated in the Ca(2+)-free medium. The inhibition of 22Na uptake observed in the presence of amiloride was the same in both types of cells in the presence or absence of external Ca2+. The findings suggest that Na entry into immature salivary cells of newborn rats is quantitatively similar to that in mature cells, but that the contribution of the loop diuretic-sensitive co-transporter and of the amiloride-sensitive Na/H exchange to Na+ entry is less in the immature cells. Na entry in the immature cells is likely to occur, therefore, primarily by other mechanisms such as Ca(2+)-regulated channels.
authors.affiliation: Center for Basic and Applied Medical Research, Lovelace Medical Foundation, Albuquerque, NM 87108.
authors.forename: S
authors.initials: S
authors.lastname: Barker
authors.forename: J R
authors.initials: JR
authors.lastname: Martinez
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000367:Age Factors; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002034:Bumetanide / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008985:Monensin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics*; D012979:Sodium Radioisotopes; D013363:Submandibular Gland / Q000166:cytology / Q000378:metabolism*
chemical_list: D012979:Sodium Radioisotopes; D002034:Bumetanide; D000001:Calcimycin; D000584:Amiloride; D008985:Monensin; D012964:Sodium; D007545:Isoproterenol; D000109:Acetylcholine; D002118:Calcium