Calcitonin gene-related peptide activates different signaling pathways in mesenteric lymphatics of guinea pigs

Abstract

The effects of calcitonin generelated peptide (CGRP) on constriction frequency, smooth muscle membrane potential (V m), and endothelial Vm of guinea pig mesenteric lymphatics were examined in vitro. CGRP (1-100 nM) caused an endothelium-dependent decrease in the constriction frequency of perfused lymphatic vessels. The endothelium-dependent CGRP response was abolished by the CGRP-1 receptor antagonist CGRP-(8 -37) (1 M) and pertussis toxin (100 ng/ml). This action of CGRP was also blocked by the nitric oxide (NO) synthase inhibitor N G -nitro-Larginine (L-NNA; 10 M), an action that was reversed by the addition of L-arginine (100 M). cGMP, adenylate cyclase, cAMP-dependent protein kinase (PKA), and ATP-sensitive K ϩ (K ATP ϩ ) channels were all implicated in the endothelium-dependent CGRP response because it was abolished by methylene blue (20-5-isoquinolinesulfonamide-dichloride (H89; 1 M) and glibenclamide (10 M). CGRP (100 nM), unlike acetylcholine, did not alter endothelial intracellular Ca 2ϩ concentration or V m. CGRP (100 nM) hyperpolarized the smooth muscle Vm, an effect inhibited by L-NNA, H89, or glibenclamide. CGRP (500 nM) also caused a decrease in constriction frequency. However, this was no longer blocked by CGRP-(8 -37). CGRP (500 nM) also caused smooth muscle hyperpolarization, an action that was now not blocked by L-NNA (100 M). It was most likely mediated by the activation of the cAMP/PKA pathway and the opening of K ATP ϩ channels because it was abolished by H89 or glibenclamide. We conclude that CGRP, at low to moderate concentrations (i.e., 1-100 nM), decreases lymphatic constriction frequency primarily by the stimulation of CGRP-1 receptors coupled to pertussis toxin-sensitive G proteins and the release of NO from the endothelium or enhancement of the actions of endogenous NO. At high concentrations (i.e., 500 nM), CGRP also directly activates the smooth muscle independent of NO. Both mechanisms of activation ultimately cause the PKA-mediated opening of K ATP ϩ channels and resultant hyperpolarization. smooth muscle; endothelium; nitric oxide; adenosine 3Ј,5Ј-cyclic monophosphate-dependent protein kinase; vasomotion CALCITONIN GENE-RELATED PEPTIDE (CGRP), like substance P, is a dominant neurotransmitter in vascular sensory nerves and is a potent vasodilator, which may play a role in modulation of total peripheral resistance of the systemic circulation (6,22,30). The pathways by which CGRP produces vasodilation vary between vascular beds. In the majority of blood vessels, application of CGRP has been reported to cause dilation through an endothelium-independent process. These vessels include cat cerebral (16, 48), rat mesenteric (1, 20, 25, 35), rat stomach mucosal (27), rabbit jejunal (34), dog basilar (40), dog lingual (33), and human uterine arteries (5). A primary signal transduction pathway involved in this form of CGRP activation is adenylate cyclase, which increases cAMP and cAMP-dependent protein kinase (PKA)-activating K ϩ channels including ATP-sensitive K ϩ (K ATP ϩ ) channels (37,...

Glucose and Glucose Transporters Regulate Lymphatic Pump Activity through Activation of the Mitochondrial ATP-Sensitive K+ Channel

“…Thus activation/deactivation of K ATP located on the plasma membrane signifi cantly contributed to the regulation of lymphatic activity [8][9][10][11][12][13]. In the present study, the vessels were pressurized for the production of spontaneous activity of smooth muscles in the thoracic ducts, as well as previous studies [9][10][11][12].…”

“…The presence of mitochondria and glycogen granules seems to produce ATP in the lymphatic smooth muscles with spontaneous activity. These morphological fi ndings may be associated with fi ndings that lymphatic smooth muscle cells have ATP-sensitive K + channels (K ATP ), which contribute to the regulation of functions including the formation of membrane potentials, maintenance of myogenic tone, and contractility and/or frequency of lymph pump activity [8][9][10][11][12][13]. We have shown that the mechanical activities of lymphatic smooth muscles are governed by metabolic dependent regulatory mechanisms, such as the intracellular concentration of ATP.…”

Postinfarction healing dynamics in the mechanically unloaded rat left ventricle

“…First, it is well known that sympathetic sprouting is important for infarct healing and scar formation, especially in angiogenesis and lymphangiogenesis (3,4,20), whereas the murine HTx preparation is devoid of innervation and lacks communication with cervical ganglions and the central nervous system. Therefore, its potential impact on the inflammatory response and on cardiac neural stem cell function (10) during LV unloading cannot be clarified in the present work.…”

Calcium sensitivity and cooperativity of permeabilized rat mesenteric lymphatics

“…This combination of smooth and striated muscle contractile elements present in lymphatic muscle could provide unique contractile characteristics (i.e., Ca 2ϩ sensitivity and cooperativity) for lymphatic myofilaments. Although numerous mechanical (3,12,30,35,49) and neurohumoral (1,2,19,31,46,50) factors have been shown to modulate the tonic and phasic activity of collecting lymphatics, few investigations of the basic contractile properties of the lymphatic myofilament have been published.…”