G-protein- and capacitatively regulated Ca2+ entry pathways are activated by muscarinic receptor stimulation in a human submandibular ductal cell line.
In the human submandibular ductal cell line (HSG) thapsigargin and carbachol stimulated Ca2+ release from the internal Ca2+ pool, resulting in the activation of capacitatively regulated Ca2+ entry (CRCE). This entry pathway was permeant to both Ca2+ and Mn2+, blocked by Ni2+ and insensitive to the muscarinic antagonist, atropine. Carbachol also stimulated an increase in cytosolic [Ca2+] in internal Ca(2+)-pool-depleted (i.e. thapsigargin-treated) cells which was dependent on the presence of external Ca2+ and blocked by Ni2+, demonstrating that it was due to Ca2+ entry. However, under the same experimental conditions, carbachol was unable to stimulate Mn2+ entry. Additionally, this latter carbachol-stimulated Ca2+ entry pathway was blocked by atropine. Pretreatment of HSG cells with AlF4-increased basal rates of Mn2+ entry due to CRCE activation, but attenuated carbachol-stimulated Ca2+ entry into thapsigargin-treated cells. The data suggest that two distinct divalent cation entry pathways are activated in muscarinic-receptor-stimulated HSG cells; a CRCE mechanism, permeable to both Mn2+ and Ca2+, and a second entry mechanism, permeable only to Ca2+. The latter does not depend on internal pool depletion, but appears to be regulated via G-protein activation.
Kaplan
M D
MD
Clinical Investigations and Patient Care Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892.
Taylor
S E
SE
Ambudkar
I S
IS
D017607:Aluminum Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002460:Cell Line; D005459:Fluorides / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D009532:Nickel / Q000494:pharmacology; D011976:Receptors, Muscarinic / Q000378:metabolism*; D013363:Submandibular Gland / Q000378:metabolism*; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
D017607:Aluminum Compounds; D011976:Receptors, Muscarinic; D013729:Terpenes; D019284:Thapsigargin; D009532:Nickel; D002217:Carbachol; D019204:GTP-Binding Proteins; D005459:Fluorides; D002118:Calcium; C032311:aluminum fluoride