Temperature-dependent modification of divalent cation flux in the rat parotid gland basolateral membrane

• Published in: The Journal of membrane biology Vol. 141; no. 3; p. 289
• Main Authors: Lockwich, T P, Kim, I H, Ambudkar, I S
• Format: Journal Article
• Language: English
• Published: United States 01.09.1994
• Subjects: Animals; Biological Transport; Calcium - metabolism; Cations, Divalent - metabolism; Cell Membrane - drug effects; Cell Membrane - metabolism; Dicyclohexylcarbodiimide - pharmacology; Fura-2; Kinetics; Male; Manganese - metabolism; Parotid Gland - metabolism; Rats; Rats, Wistar; Spectrometry, Fluorescence; Temperature; Thermodynamics; Trypsin - pharmacology
• ISSN: 0022-2631; 1432-1424
• DOI: 10.1007/BF00235138

Divalent cation (Mn2+, Ca2+) entry into rat parotid acinar cells is stimulated by the release of Ca2+ from the internal agonist-sensitive Ca2+ pool via a mechanism which is not yet defined. This study examines the effect of temperature on Mn2+ influx into internal Ca2+ pool-depleted acini (depl-acini, as a result of carbachol stimulation of acini in a Ca(2+)-free medium for 10 min) and passive 45Ca2+ influx in basolateral membrane vesicles (BLMV). Mn2+ entry into depl-acini was decreased when the incubation temperature was lowered from 37 to 4 degrees C. At 4 degrees C, Mn2+ entry appeared to be inactivated since it was not increased by raising extracellular [Mn2+] from 50 microM up to 1 mM. The Arrhenius plot of depletion-activated Mn2+ entry between 37 and 8 degrees C was nonlinear, with a change in the slope at about 21 degrees C. The activation energy (Ea) increased from 10 kcal/mol (Q10 = 1.7) at 21-37 degrees C to 25 kcal/mol (Q10 = 3.0) at 21-8 degrees C. Under the same conditions, Mn2+ entry into basal (unstimulated) cells and ionomycin (5 microM) permeabilized depl-acini exhibit a linear decrease, with Ea of 7.8 kcal/mol (Q10 = 1.5) and 6.2 kcal/mol (Q10 < 1.5), respectively. These data suggest that depletion-activated Mn2+ entry into parotid acini is regulated by a mechanism which is strongly temperature dependent and distinct from Mn2+ entry into unstimulated acini.