Relationship Between the Levels of Intracellular Cyclic Nucleotides and Mechanical Responses Induced by Drugs

Abstract

Abstract-The tracheal smooth muscle dissected free from connective tissues was used as a test preparation, since isoprenaline caused a decrease in cyclic GMP in the muscle while it caused an increase in cyclic GMP in the remaining tracheal tissue. Acetylcholine, histamine and papaverine increased both cyclic AMP and cyclic GMP levels in the tracheal muscle. Isoprenaline increased the cyclic AMP level but decreased the cyclic GMP level. However, when tracheal muscle was incubated with isoprenaline in the presence of acetylcholine, isoprenaline did not cause a decrease in cyclic GMP but rather a significant increase in cyclic AMP after only 1 min incubation. These results indicate that the relaxation of the tracheal muscle by isoprenaline is initiated by the increase in cyclic AMP but is not associated with the change in cyclic GMP.Several authors have reported that elevation of the intracellular cyclic AMP level is associated with relaxation of smooth muscle induced by isoprenaline or papaverine (1, 2, 3, 4, 5, 6). It has also been reported that acetylcholine and other muscarinic receptor stimulants increase the intracellular level of cyclic GMP in mammalian heart muscle, brain, lung slices and intestinal smooth muscle (2,7,8,9,10,11). Recently, Murad and Kimura (12) tested the effects of several drugs on cyclic AMP and cyclic GMP levels in incubations of guinea pig tracheal ring preparations and concluded that drugs which can relax the tracheal muscle increased the cyclic AMP level and drugs which can contract the muscle increased the cyclic GMP level. It is, however, well known that the tracheal smooth muscle contracted by acetylcholine is relaxed by beta-adrenomimetics. Therefore, the aim of the present work was to test changes in cyclic AMP and cyclic GMP levels involved in antagonism between acetylcholine and isoprenaline. MATERIALS AND METHODSFemale Hartley guinea pigs (250-350 g in body weight) were sacrificed by a blow on the head and then bled from the femoral artery. The trachea was isolated and placed in a Locke-

Signal Transduction Pathway Involved in β3-Adrenoceptor-Mediated Relaxation in Guinea Pig Taenia Caecum

“…One piece was used for measuring the control level of cyclic AMP and the other for estimating any change of cyclic AMP concentration after treatment with the test drugs. The tissues were homogenized with a glass homogenizer in 2 ml of cold trichloroacetic acid (6% w/v) that contained 0.5 pmol of [3H]cyclic GMP to estimate the recovery of cyclic AMP (15). The homogenate was centrifuged at 3000 rpm at 01C for 15 min, the supernatant was then acidified with 1 N HC1, and the trichloroacetic acid was extracted with ether.…”

“…The cyclic AMP samples were lyophilized. The lyophilized samples were dissolved with sodium acetate buffer, pH 6.2, and they were used for the estimation of cyclic AMP and for calculating the recovery (15). The quantity of cyclic AMP was determined by a radioimmunoassay, using a commercial kit (Yamasa, Chiba).…”

Vasoactive Intestinal Polypeptide Promotes Cyclic Adenosine 3‘,5’‐mono‐phosphate Accumulation in Guinea‐pig Trachea

“…In this work, we have attempted to characterize the mode of action of VIP on tracheobronchial smooth muscle by measuring VIP-mediated cyclic adenosine 3',5'-monophosphate (cyclic AMP) accumulation in this tissue. A number of agents stimulate the production of cyclic AMP, or inhibit its degradation, in the airways (Andersson, Bergh & Svedmyr, 1972;Inamasu, Shinjo, Iwasawa & Morita, 1974;Murad, 1974;Duncan, Griffin & Solomon, 1975;Ohkubo, Takayanagi & Takagi, 1976;Triner, Velliemoz & Verosky, 1977), and these actions may be related to their ability to produce bronchodilatation (Said et al, 1974;Andersson et al, 1972;Inamasu et al, 1974;Murad, 1974;Duncan et al, 1975;Ohkubo et al, 1976;Triner, et al, 1977). The bronchodilator action of VIP is of special interest in view of the recent demonstration that a VIP-like peptide occurs in normal lung tissue (Said & Mutt, 1977).…”

Muscarinic agents modify kinetics properties of membrane‐bound guanylyl cyclase activity

“…These agents induce smooth muscle contraction by a process which appears to be associated with elevation in cGMP concentrations, however a direct causal relationship has not been established [6][7][8][9][10] and the biochemical link between the muscarinic receptor and guanylyl cyclase remains unknown [11][12][13][14][15][16][17]. We have previously shown that in isolated plasma membrane fractions from rat liver, muscarinic agents stimulate cGMP production, an effect that is inCorrespondence address: M. Alfonzo, Secci6n de Biomembranas, Instituto de Medicina Experimental, Cfitedras de Patologia General y Fisiopatologia, y Bioquimica, Facultad de Medicina, Universidad Central de Venezuela (UCV), Apartado 50587, Sabana Grande, Caracas, Venezuela hibited by atropine [18].…”