Effect of chlorpromazine on ion transport induced by cholera toxin, cyclic AMP and cyclic GMP in isolated mucosa from hen intestine

STb enterotoxin of Escherichia coli: cyclic nucleotide-independent secretion

Escherichia coli may produce a heat-labile enterotoxin (LT) or two heat-stable enterotoxins (STa, STb). Experimentally, STb is consistently active only in 5 h-weaned pig intestinal loops (WPIL), an effect that is largely removable by rinsing. At least three mechanisms initiate small intestinal secretion: cyclic AMP (LT), cyclic GMP (STa) and calcium (A23187). All three increase short-circuit current (SCC) in Ussing chambers by stimulating net Cl- secretion. STb significantly increases SCC within 2-5 minutes in Ussing chambers and is independent of cyclic AMP and cyclic GMP. When compared to crude culture filtrates of a non-toxigenic strain of E. coli, crude culture filtrates of STb did not alter Na+ or Cl- undirectional or net fluxes. However, the calculated residual ion flux (JRnet) increased significantly in STb-treated tissues and appeared to largely account for the STb-induced increase in SCC. Furosemide applied serosally (10(-3) M), the removal of extracellular calcium, and lanthanum chloride (10(-3) M) did not inhibit the effect of STb on SCC. Chlorpromazine (0.4 mM) completely inhibited STb-induced secretion in porcine loops. This inhibition was a non-specific reversal of the STb effect because in Ussing chambers, chlorpromazine simply induced an equal and opposite effect on SCC. These results indicate that STb initiates intestinal secretion in porcine jejunum in vitro by stimulating primarily non-chloride anion secretion in the absence of extracellular calcium. We postulate that STb causes bicarbonate secretion by a mechanism distinct from those of previously studied enterotoxins.

The antisecretory factor: synthesis, anatomical and cellular distribution, and biological action in experimental and clinical studies

The antisecretory factor (AF) is a 41-kDa protein that provides protection against diarrheal diseases and intestinal inflammation. Its cDNA has been cloned and sequenced. AF is highly potent, with 10(-12) mol of recombinant AF being sufficient to counteract experimentally induced diarrhea in rat. The antisecretory activity is exerted by a peptide located between positions 35 and 50 of the AF sequence. Synthetic peptides based on this sequence are promising candidates for drugs to counteract intestinal hypersecretion, as well as imbalances of fluid transport in other body compartments. AF probably exerts its effects via nerves; AF immediately and potently inhibits ion transport across isolated nerve membranes from Deiters' cells. Immunocytochemistry has shown that AF is present in most tissues in the body, and in situ nucleic acid hybridization has shown that cells that store AF are also capable of AF synthesis. The endogenous plasma level of AF is increased by enterotoxins and by certain food constituents such as hydrothermally processed cereals. These cereals significantly improve clinical performance in patients suffering from inflammatory bowel diseases. AF-enhancing food also protects domestic animals against diarrheal diseases, and such feed has been used successfully in Swedish swine farming for the past 10 years. Increased understanding of AF action might result in expanded clinical applications and confirm that AF is an important regulator of homeostasis.

Effect of chlorpromazine on experimental diarrhoea in just-weaned piglets

In just-weaned piglets (n = 30, 3-4 weeks) diarrhoea (100%) and vomiting (66%) were provoked by inoculation with transmissible gastroenteritis virus and enterotoxigenic E. coli strains (O149: K91: K88ac; LT, STa and STb enterotoxin positive). This combined infection resulted in a mortality of 71% within 7 days. During this period animals revealed a decrease in body weight, in arterial pressure, in leukocyte count, in plasma pH and in plasma lactic acid concentrations, and an increase in heart rate and in total plasma protein concentration. In shocked and expiring piglets an increase in haematocrit and a decrease in base excess and actual bicarbonate were observed. Chlorpromazine, administered intramuscularly on 3 successive days following the dual infection in 8 K88ac susceptible pigs, in a dosage of 2 and 1.5 mg/kg.24 h, somewhat retarded the appearance of severe diarrhoea and suppressed vomiting. These beneficial effects, however, did not result in an increased survival.

Serotonin-induced chloride secretion in hen colon. Possible second messengers

1. Serotonin, 100 microM, induces a peak increase in short circuit current of about 150 microA/cm2 and in cord conductance of about 7 mS/cm2 and a more prolonged increase of 30 microA/cm2 and 1.4 mS/cm2 which lasts more than 30 min in hen colon. 2. The peak increase in short circuit current and cord conductance is due to a concomitant Cl- secretion. 3. The second messenger, which mediates Cl- secretion, increases in short circuit current and cord conductance, is cyclic AMP as theophylline, 0.5 mM, increases the response in short circuit current to 1 microM serotonin from 38 +/- 5 to 78 +/- 8 microA/cm2 and in g from 1.1 +/- 0.4 to 2.0 +/- 0.3 mS/cm2. 4. Theophylline, 0.5 mM, also sensitizes the hen colon to cyclic AMP yielding an EC50 of 0.24 +/- 0.03 mM in the presence of theophylline compared with an EC50 of 2.3 +/- 0.2 mM in the absence of theophylline. 5. Manipulations of other putative second messenger systems, such as the prostaglandins/leucotrienes, the phosphoinositides and external Ca2+ or calmodulin-sensitive enzymes, did not influence the serotonin response in short circuit current and cord conductance, thus ruling out their importance as intracellular mediators.

A low-salt diet facilitates Cl secretion in hen lower intestine

The regulation of sodium and chloride transport in hen coprodeum by mineralocorticoids was investigated with isolated epithelia under short-circuit conditions. Unidirectional fluxes of Na and Cl were measured by isotopes and modulated by amiloride, theophylline and bumetanide. Hens were maintained either on low-NaCl diet (LS) or on high-NaCl diet (HS). Plasma aldosterone (PA) levels of these groups were measured with radioimmunoassay. A group of HS hens received injections of aldosterone on a 6-hr schedule before experiments. Another group of LS hens was resalinated, and experiments carried out on a 24-hr interval. Salt deprivation stimulated PA levels ninefold, compared to HS hens. Na absorption was stimulated according to previous reports. Electrogenic Cl secretion was elicited by theophylline and partially inhibited by bumetanide. Modulation of PA levels by diet, resalination or aldosterone injection changed the magnitude of electrogenic Cl secretion in parallel between 0.5 mueq/cm2.hr (HS) and 4 mueq/cm2.hr (LS), with pronounced alteration in tissue resistance. The results demonstrate a new action of aldosterone which besides stimulating Na absorption also directly or indirectly elicits Cl secretion. Evidence is presented for a hormonal adaptation of chloride transport in this epithelium. There was a morphological change of the apical plasma membrane and further experiments will have to clarify the exact cellular nature of this process.

Modulation of Na and Cl transport by mineralocorticoids

1. The epithelia of the hen lower intestine show a Na-channel, Na-cotransport, chloride cells, and chloride absorption and secretion. 2. The short circuit current is affected by low salt levels, amiloride, glucose, lysine, leucine, galactose, ouabain, bumetanide, aldosterone, dexamethasone and spironolactone. 3. The properties of the different sodium and chloride channels are described.

Electrical PD, short-circuit current and fluxes of Na and Cl across avian intestine

In vitro measurements were made of transmural potential difference (PD), short-circuit current (Isc), resistance and unidirectional fluxes of 22Na and 36Cl across the duodenum, jejunum, ileum and colon of normal sodium-replete domestic fowl (Gallus domesticus). The PD ranged from about 1 mV across the duodenum to 8 mV across the colon while the Isc was, respectively, 2.8 and 64 microA X cm-2. The jejunum and ileum exhibited values between these extremes. Unidirectional fluxes (under short-circuit conditions) of Na and Cl were lowest across the duodenum where there was no evidence of active transport of these ions. Unidirectional fluxes of Na and Cl were less across the jejunum than across the ileum or colon. A net active transport of Na (but not Cl) was observed in the ileum (= 106% of the Isc) and colon (= 50% of Isc). The possible physiological significance of these observations in the domestic fowl are discussed and are compared to that of a mammal, the rabbit.

The susceptibility of Plasmodium falciparum in vitro to chlorpromazine and the stereo-isomeric compounds cis(Z)- and trans(E)-clopenthixol

New antimalaria drugs are needed on the background of increasing resistance to chloroquine. This study was undertaken to elucidate whether other membrane stabilizers than chloroquine have anti-malarial activity in vitro. We here report the anti-plasmodial activity of chlorpromazine (CPZ) and the stereo-isomeric compounds cis(Z)- and trans(E)-clopenthixol. As a screening method we used a modified Desjardins' 3H-hypoxanthine assay. The IC50 = 50% inhibition of 3H-hypoxanthine uptake was found at 1.028 ng/ml = 3.2 microM CPZ, 758 ng/ml = 1.6 microM trans(E)-clopenthixol and 436 ng/ml = 0.9 microM cis(Z)-clopenthixol. The inhibitory effect of trans(E)-clopenthixol in these low concentrations on Plasmodium falciparum in vitro seems particularly promising, since it is known that trans(E)-clopenthixol has no neuroleptic effect.

The antibacterial effect of selected neuroleptics on Vibrio cholerae

The present investigation has been undertaken to illustrate the anti-bacterial effect of chlorpromazine, clopenthixol and levomepromazine-maleate. It has been shown that clopenthixol has the strongest antibacterial effect. It is known that chlorpromazine also has an antisecretory activity. The fact that clopenthixol exists in cis(Z)- and trans(E)-isomerical compounds, and that these compounds both have an antibacterial effect, but only the cis-compound has an antisecretory and neuroleptic effect, might suggest the development of more specific pharmaceuticals in these new fields.

Differentiation of secretagogue drugs by chlorpromazine in rat intestine in vivo

The effect of chlorpromazine (CPZ) on passive epithelial permeability and net fluid movement induced by secretagogues was tested in the rat intestine in vivo. CPZ, in a dose of 20 mg/kg intramuscularly, did not alter colonic permeability either in control conditions or during increased permeability caused by deoxycholic acid (DOC) or bisacodyl. Fluid secretion induced by cholera toxin and theophylline was strongly reduced by CPZ. The effects of oxyphenisatin and bisacodyl were only slightly but significantly inhibited by CPZ, whereas the action of DOC was unaffected. It is concluded, that the increase of the epithelial permeability is the main reason for the augmented fluid secretion caused by DOC. Bisacodyl and oxyphenisatin seem to act partly via an increase in permeability and to some degree via an induction of an active secretory process.

Enterotoxigenic diarrhea: mechanisms and prospects for therapy

Studies over the past decade have led to a rudimentary but working knowledge of intestinal electrolyte transport. Purification of bacterial exotoxins has allowed an understanding of how these agents stimulate cells. Coupled NaCl influx processes and chloride secretory mechanisms have been shown to be affected by exotoxin-stimulated increases in cyclic nucleotides, as well as by increases in intracellular calcium and arachidonic acid metabolites. Catecholamines, somatostatin, phenothiazines, nonsteroidal anti-inflammatory drugs, and opiates appear to be the most promising of the antisecretory drugs. While the mechanism of action of these agents remains to be determined, there is significant hope that effective antisecretory drugs will emerge in the near future.

Reversal of enterotoxic diarrhoea by anaesthetic and membrane-stabilizing agents

The effect of membrane-stabilizing and sedative drugs on enterotoxic diarrhoea was studied in mice. Fluid secretion was induced in ligated loops of the small intestine by challenge with cholera toxin (CT), heat-labile enterotoxin (LT) from Escherichia coli or dibuturyl-cyclic AMP (dB-cAMP). Chlorpromazine, melperone, diazepam, mebumal, ketamine and ethanol all inhibited CT-induced hypersecretion. ED50 being 1.5, 4, 4, 35, 70 and 1500 mg/kg, respectively. The drugs also blocked CT-stimulation of adenylate cyclase, which mediates the action of CT. Concomitant with the antisecretory effect a sedative effect was induced, as judged by the motility and righting reflex of the animals. Hypersecretion by E. coli and LT was also totally blocked by chlorpromazine, diazepam, ketamine and ethanol. In contrast, the secretion by dB-cAMP which bypasses adenylate cyclase in its action, was not affected by diazepam and was only partly reversed by chlorpromazine, ketamine and ethanol. The reversal of dB-cAMP-secretion is probably due to enhanced absorption, rather than inhibition of adenylate-cyclase. The use of membrane-stabilizing drugs may represent a new principle for pharmacological treatment of diarrhoea.

NaCl transport across hen colon. Dependence on electro-chemical driving force

1. Sheets of isolated mucosa from the colon of chickens on either a high or a low NaCl diet were mounted in Ussing chambers. They were bathed in Krebs-phosphate medium and exposed to sodium concentrations ranging from 3.0 to 140 mmol/l (choline-chloride replacement). 2. In the short-circuited state the net fluxes of sodium in the mucosa (m)-serosa (s) direction, followed saturation kinetics with Km = 25 mmol/l in the low-NaCl chickens and 124 mmol/l in the high-NaCl chickens. 3. The unidirectional fluxes of sodium in the s-m direction were linearly related to the electro-chemical driving force. The apparent permeabilities were 8.6 +/- 0.3 x 10(-6) cm/s in the low-NaCl and 11.6 +/- 0.3 x 10(-6) cm/s in the high-NaCl birds. 4. The chloride fluxes were in the short-circuited state of equal magnitude in the m-s and the s-m direction, and in the two dietary states. Changes in the electrical driving force resulted in changes in chloride fluxes compatible with passive flow.

A study of inhibition of cholera toxin-induced intestinal hypersecretion by neuroleptics

Various types of neuroleptics and other agents were examined for inhibitory effect in cholera toxin-induced hypersecretion in ligated loops of mice jejunum. Several agents belonging to the phenothiazine group or thioxanthene group were inhibitory. Only three other neuroleptics, loxapin, haloperidol and penfluridol, inhibited the hypersecretion. Among the miscellaneous agents the calcium antagonist nifedipine was inhibitory. The potencies of the neuroleptics did not correlate with the dopamine antagonistic potencies. The results indicate that the site of antisecretory action of the drugs is to be found outside the central nervous system.

Effects of chlorpromazine on fluid transport across the intestinal mucosa of the rat

The effect of chlorpromazine (CPZ) on net fluid transport in the small intestine of the rat was studied, using a ligated loop model. Given intramuscularly at 5 mg/kg, CPZ induced a 50% increase of net fluid absorption in jejunum, but had no effect in ileum. Similarly, the drug decreased net fluid accumulation induced by dibutyryl-cyclic AMP in jejunum, but did not influence net fluid accumulation in ileum. In contrast, net fluid accumulation induced by cholera toxin was decreased by CPZ in both jejunum and ileum. Inhibition of cyclic AMP (cAMP)-which probably mediates the hypersecretion by the toxin-was also noted. These results suggest that CPZ reverses fluid transport during cholera in two ways: by a cAMP-independent enhancement of fluid absorption in jejunum and by inhibition of the toxin-induced cAMP-production in jejunum as well as ileum. Each of these processes may be independently affected by pharmacological substances and subjected to neural and hormonal regulation.