Smooth muscle preparations

Although in in vivo circumstances an intracellular free calcium increase apparently acts as the primary modulator of contraction, it can be bypassed in highly permeabilized smooth muscle preparations where the active subunit of MLCK can be introduced to phosphorylate myosin and induce contraction. The MLCK catalyzed phosphorylation of serine-19 is seen as the necessary event in the activation of smooth muscle myosin to form crossbridges. Thus, the rising phase of force during an isometric smooth muscle contraction follows an increase in the degree of phosphorylation of myosin, and that in turn follows the transient rise of (a) cytosolic free Ca, (b) Ca-calmodulin complexes, and (c) the active form of MLCK. The regulation of the intracellular calcium is discussed below. The dynam-... 

AMOS s, OKWUASABA F K, GAMANIEL K, AKAH P, WAMBEBE c (1998) Inhibitory effects of the aqueous extract of Pavetta crassipes leaves on gastrointestinal and uterine smooth muscle preparations isolated from rabbits, guinea pigs and rats. J Ethnopharmacol. 61 209-13. 

Somlyo It is possible in smooth muscle preparations to do high frequency stimulation of nerves, and get a contraction that is abolished by TTX. This suggests that the transmitter does get to the smooth muscles. This is a physiological experiment. 

N, O-Diacylated or O-alkylated N-hydroxysulfonamides release nitroxyl (HNO) upon hydrolysis or metabolic dealkylation, as determined by gas chromatographic identification of nitrous oxide in the reaction headspace [27-29, 38]. Scheme 7.5 depicts the decomposition of a representative compound (7) to a C-acyl nitroso species that hydrolyzes to yield HNO. Either hydrolysis or metabolism removes the O-acyl or O-alkyl group to give an N-hydroxy species that rapidly decomposes to give a sulfinic acid and an acyl nitroso species. This C-acyl nitroso species (8) hydrolyzes to the carboxylic acid and HNO (Scheme 7.5). These compounds demonstrate the ability to relax smooth muscle preparations in vitro and also inhibit aldehyde dehydrogenase, similar to other HNO donors [27, 29]. 

Delayed constrictor responses in guinea pig smooth muscle preparations following challenge with jute extract have been observed. The response diminishes with successive doses of extract as though some "store" is being depleted, until, finally, constriction is not seen. Cotton extract is a more potent contracting agent than jute. 

The most recent reports on the action of the water soluble toxin from G, toxicus concluded that this toxin, referred to as maitotoxin, invokes an unmediated stimulatory (contractile) response on contact with guinea pig ileal smooth muscle preparations. Furthermore, this response was said to be due to an activation of calcium channels in the smooth muscle membranes (J7). Previous studies of this toxin from the same source indicated that it produces an inhibitory effect on guinea pig atrial muscle (28, 19). 

The present study reports on the effects of the water soluble toxin from toxicus from the Caribbean on guinea pig ileal smooth muscle preparations. It also compares the results obtained from the water soluble toxin with those obtained using lipid extraction. 

Lukanov J, Atmadjov P. 1979. Investigating the effect of silver ions on the contractile function of smooth-muscle preparations from guinea pig stomach, in vitro. Folia Med (Plovdiv) 21 11-19. 

Takatonine (5,6,7,4 -tetramethoxy-l-benzylisoquinoline) had a weak atropine-like and papaverine-like effect (370). Its spasmolytic activity was determined on isolated smooth muscle preparations of guinea pig ileum and mouse small intestine. 

Ketotifen is a nonspecific, oral, mast cell stabilizer introduced in 1972 (1). The prominent biochemical-pharmacological activities of ketotifen are H,-receptor antagonism, phosphodiesterase inhibition, inhibition of the formation SRS-A, and inhibition of calcium flux in smooth muscle preparations all these actions are suited to prevent a development of asthmatic conditions. Promising results were obtained in early clinical trials ketotifen was equipotent with disodium cromoglycate in prevention of asthma induced by spontaneous excer-cise or by antigens. Also, ketotifen is more specific than clemastine as a H-,-receptor antagonist. However, more recent, controled trials failed to substantiate the early therapeutic optimism. The beneficial effect of ketotifen in the treatment of asthma is only small it was noted that this effect is associated with pronounced sedation (2). 

Based on this, one would predict that treatment of intact smooth muscle preparations with an inhibitor of CaMKII should potentiate myosin light chain phosphorylation and the rapid phase of force development. In contrast, we have found that in carotid arterial smooth muscle, KN-93 inhibition of CaMKII activation in response to physiological contractile stimuli correlates with a marked inhibition of tonic force responses (Rokolya and Singer 2000), suggesting an alternative dominant action of CaMKII on the smooth muscle contractile apparatus. 

Egle JL Jr. 1973. Pressor effects of 4 aliphatic aldehydes and their interactions with carbon-14 norepinephrine in an isolated smooth muscle preparation. Fed Proc32(3 Part 1) 795. 

Anderson (1978) recommended the rabbit detrusor muscle as an unique in vitro smooth muscle preparation. Rabbit detrusor muscles are thin and devoid of underlying submucosal tissue with parallel fiber orientation. The tissue exhibits autorhythmicity, characteristic of most single unit type smooth muscle preparations and can be employed in either isometric or isotonic organ bath recording systems. 

Anderson GF (1978) The rabbit detrusor muscle a unique in-vitro smooth muscle preparation. J Pharmacol Meth 1 177-182... 

Vassilev et al. (1993) exposed Wistar rats to subtoxic doses of Co2+ or Ni2+, receiving Co(N03)2 or NiS04 with drinking water for 30 days, and measured the changes in the contractile responses to carbachol and in the inhibitory effects of verapamil and nitrendipine on isolated smooth muscle preparations of the ileum and the trachea. 

It was found that only one pharmacophore is required for the k opioid antagonist selectivity of nor-BNI [136]. In smooth muscle preparations, the meso isomer (81) (derived from (-)-naltrexone and its inactive (+)-enantio-mer [27]) of nor-BNI was more potent than nor-BNI and about half as selective as k antagonist. Since (81) contains one antagonist pharmacophore but yet retains some k selectivity, it was concluded that k selectivity is not de-... 

Table 3 Opioid antagonist and agonist potencies of selected pyrido- and thienomorphinans derivatives in the MVD and GPI smooth muscle preparations...

P2X, receptors show an order of potency for the natural ligands ATP > ADP and the unnatural ligands a.P-methylene-ATP and ATP-y-S are useful investigational agonists, but desensitization is very evident. These receptors are found in a number of smooth muscle preparations including arterioles, vas deferens and the urinary bladder, where they cause depolarization and contraction. They are found only in neonate brains. The form of the receptor here seems to be a homopolymer formed of identical units. At these sites, the ejps (excitatory junction potentials) seen on sympathetic nerve stimulation are caused in response to ATP action at P2X purinoceptors when it is liberated - as a cotransmilter - from sympathetic varicosities. 

The subtype of muscarinic receptor in the smooth muscle has been characterized as M3 by use of selective anticholinergics and different smooth muscle preparations from different species. These smooth muscle tissues include (l)trachea (22), ileum (23, 24), uterine artery (25), and submucosal arterioles of guinea pig (26) (2) aorta (27) and coronary artery of rabbit (28) and (3) trachea (29), aorta (30), and iris (3 l)of rat. Human uterine arteries (32), airways (33), and ciliary muscles (34) have also been shovm to contain the M3 type of muscarinic receptors. 

Z3.3 In Vitro AsKiys for Efficacy. Until the cloning of the opioid receptors isolated tissue preparations, particularly smooth muscle preparations, were used extensively to characterize opioids (see Refs. 131,132 for reviews). The electrically stimulated GPI myenteric plexus-longitudinal muscle and the MVD... 

Recently, the Leu-enkephalin analog containing a novel derivative of Dmt lacking a basic amine [(2(S )-2-methyl-3-(2,6-dimethyl-4-hydroxyphenyDpropanoic acid, (2S)-Mdp, Fig. 7.431 was reported this peptide is an antagonist in both the MVD and GPI smooth muscle preparations, with fivefold higher potency in the MVD (739). 

OFQ/N and the ORLl receptor are also involved in a number of other physiological effects (see Refs. 87,891. One of the most significant effects is the anxiolytic activity of OFQ/N (1013), which has been postulated to be one of OFQ/N s most fundamental actions, and may help explain the effects of OFQ/N on other phenomena [e.g., locomotion, reward, and feeding (87)]. A small molecule ORLl agonist has also demonstrated anxiolytic activity (1014), demonstrating an important potential therapeutic application of these compounds. Like opioids, OFQ/N inhibits electrically induced contractions in the GPI and MVD smooth muscle preparations these effects are... 

Early studies of the pharmacology of the ORLl system were hindered by the lack of antagonists for this receptor. Therefore there was considerable excitement in the field when the first report of an antagonist appeared in the literature (1024). The reduced amide derivative of OFQ/N [Phe i/f(CH2NH)Gly ]0FQ/ N-(1-13)NH2 (262, Fig. 7.51 referred to as [F/G]NC(1-13)NH2 by Calo and coworkers), which was synthesized to protect the peptide from metabolism by aminopeptidases, was initially reported to be an antagonist of OFQ/N-(1-13)NH2 in smooth muscle preparations... 

Mahmoudian M, Richards WG. QSAR of binding of dihydropyridine-type calcium antagonists to their receptor on ileal smooth muscle preparations. J Pharm Pharmacol 1986 38 272-6. 

The phenyl phosphonate N-0164 antagonizes PGE2 and PGF2a on several smooth muscle preparations and prevents PGE2 induced diarrhea in mice13f. The prostanoid HR-546 antagonizes PGE2 induced smooth muscle contractions with an EDjq 100 times lower than that of 7-oxa-13-prostynoic acid. ... 

However, these compounds all act as partial agonists in smooth muscle preparations. Further work produced compounds more distinct in structure from TXA2, such as the 7-oxabicyclo[2.2.1]heptane analog, SQ29548... 

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