Macrophages express functional receptors for calcitonin-gene-related peptide.
The present study was designed to investigate whether non-activated macrophages express calcitonin (CT) or calcitonin-gene-related peptide (CGRP) receptors. To this end, we first analyzed whether CT and CGRP induce a cAMP accumulation in macrophages. Macrophages were treated for 2 min with increasing concentrations of either CT or CGRP in the presence or absence of IBMX. A dose-dependent cAMP accumulation was measured in response to CGRP with a half-maximal effect attained with 1 nM CGRP. CT failed at all doses to induce an accumulation of cAMP. The effects of CT and CGRP on the activation of the Na-H exchanger were next assessed by spectrofluorometry by using the pH-sensitive dye 2,7 biscarboxyethyl-5(6)-carboxyfluorescein (BCECF). Steady-state pHi of macrophages in a 7.4, HCO3-free solution (HEPES-buffered) was 7.04 +/- 0.08 (n = 22). pHi recovery following an NH4+/NH3 acid load was inhibited by the removal of Na+ or by the addition of the amiloride analog EIPA; therefore recovery is dependent on Na-H exchange activity. CT had no effect on steady-state pHi but CGRP increased pHi in a dose-dependent fashion (10(-12) to 10(-6) M). The pHi change induced by CGRP was due to the stimulation of the Na-H exchanger as CGRP enhanced the rate of recovery (dpHi/dt) from an acid load from 45.3 to 77.2 microMs-1 (n = 8, P less than 0.002) and was completely blocked by EIPA. These data indicate that CGRP both enhances the activity of the Na-H exchanger and increases intracellular cAMP, thus demonstrating that macrophages express functional CGRP receptors.
Vignery
A
A
Department of Orthopaedics and Rehabilitation, West Haven V.A. Medical Center, Yale University School of Medicine, New Haven, Connecticut 06510.
Wang
F
F
Ganz
M B
MB
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002116:Calcitonin / Q000494:pharmacology; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism* / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008264:Macrophages / Q000737:chemistry / Q000378:metabolism*; D010529:Peritoneal Cavity / Q000166:cytology; D051381:Rats; D018003:Receptors, Calcitonin; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers; D013110:Sphingosine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D002352:Carrier Proteins; D018003:Receptors, Calcitonin; D011956:Receptors, Cell Surface; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; D002116:Calcitonin; D000242:Cyclic AMP; D015740:Calcitonin Gene-Related Peptide; D013110:Sphingosine; D013755:Tetradecanoylphorbol Acetate; D015056:1-Methyl-3-isobutylxanthine; C039614:ethylisopropylamiloride