RT Journal Article
SR Electronic
T1 Guanine nucleotide binding proteins may modulate gating of calcium channels in vascular smooth muscle. I. Studies with fluoride.
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 343
OP 351
VO 250
IS 1
A1 Zeng, Y Y
A1 Benishin, C G
A1 Pang, P K
YR 1989
UL http://jpet.aspetjournals.org/content/250/1/343.abstract
AB Fluoride (F-), a known stimulator of G-proteins, was used to examine the relationship between G-proteins and calcium channels (CaC) in rat vascular smooth muscle (VSM). Treatment of isolated rat tail artery helical strips with F- (2.5-20 microM) produced a Ca++-dependent contraction. In the absence of added AlCl3, subthreshold NaF shifted the KCl, as well as the arginine vasopressin and norepinephrine concentration-related tension curves to the left. Nifedipine and verapamil, known CaC blockers, inhibited the NaF-related contraction. AlCl3 (20 microM), which is required for G-protein stimulation by F-, strikingly potentiated the contractile response to F-. The NaF-induced contraction was relaxed by 3-isobutyl-1-methylxanthine as well as by forskolin and by dibutyryladenosine-cyclic AMP, and the effect therefore may be independent of cAMP. 45Ca-uptake was elevated by NaF, and partially blocked by nifedipine and verapamil. NaF also inhibited the basal and forskolin-stimulated cAMP production, suggesting that F- stimulated the putative Gi in the intact VSM cells. NaF stimulated accumulation of IP in a concentration-dependent manner, indicating that F- stimulated the putative G-protein Gp which couples various receptors to hydrolysis of phosphoinositides and mobilization of Ca++. These results indicate that NaF-induced vasoconstriction is related to the opening of the CaC in the plasma membrane and perhaps a subsequent entry of the extracellular Ca++ into the cell.(ABSTRACT TRUNCATED AT 250 WORDS)