The influence of bisacodyl and deacetylbisacodyl on mucus secretion, mucus synthesis and electrolyte movements in the rat colon in vivo

Desacetyl bisacodyl-induced epithelial Cl(-) secretion in rat colon and rectum

The purpose of this study was to clarify the mode of desacetyl bisacodyl (DAB)-induced secretory action in intestinal tissues using an Ussing chamber assay. DAB is the active metabolite of the laxative bisacodyl. In mucosal-submucosal preparations, mucosal application of DAB induced a transient decrease followed by subsequent increases in short-circuit current and tissue conductance in a concentration-dependent manner. DAB-induced responses occurred from the middle colon to the rectal segment but not in the proximal colon. Moreover, these responses were not observed under chloride (Cl(-))-free conditions or in the presence of DAB on the serosal side of the mucosalsubmucosal specimens. Treatment with tetrodotoxin had no effect on the DAB-induced responses; however, mucosal treatment with a COX inhibitor piroxicam resulted in the elimination of responses. These results suggest that DAB may contribute to the laxative action by inducing Cl(-) secretion which is associated with the COX signaling pathway. This study also demonstrated that the DAB target molecule is present on the mucosal side from the middle colon to the rectal segment.

Effects of bisacodyl on ascending colon emptying and overall colonic transit in healthy volunteers

BACKGROUND

The mechanism of action of bisacodyl in the unprepared human colon remains unclear.

AIM

To evaluate the effect of oral bisacodyl on the overall and regional colonic transit in humans.

METHODS

In a double-blind, randomized, placebo-controlled study of 25 healthy participants, effects of oral bisacodyl (5 mg p.o. per day) and placebo on colonic transit were compared. A validated scintigraphy method was used to measure colonic transit. The primary transit endpoints, ascending colon emptying t(1/2) and geometric centre of colon isotope at 24 h (overall transit), were compared (Wilcoxon rank sum test).

RESULTS

There were significant treatment effects on ascending colon t(1/2), with the bisacodyl group demonstrating accelerated emptying [median 6.5 h, interquartile range 5.0-8.0 h] relative to the placebo group [11.0 h (7.0-17.1); P = 0.03]. Numerical differences in colonic geometric centre 24 h [bisacodyl median 3.0 (2.2-3.8), placebo 4.0 (3.1-4.6)] were not significant (P = 0.19). There were no significant differences observed in geometric centre 4 h.

CONCLUSION

Oral 5 mg bisacodyl accelerates ascending colon in the unprepared colon in healthy adults; this action may contribute to the drug's efficacy in constipation.

Short chain fatty acids but not lactate or succinate stimulate mucus release in the rat colon

BACKGROUND

Short chain fatty acids (SCFAs) affect various intestinal functions. Mucus is an important physiological component of the intestinal mucosal barrier. However, the effect of SCFAs or other organic acids on the intestinal mucus release is poorly understood. The aim of this study was to investigate whether lumen SCFA stimulates mucus release into the rat colon.

METHODS

A solution of SCFA, lactate or succinate was infused into the colon of anesthetized rats, and we then measured the hexose content of the effluent. We also examined the influence of cholinergic antagonists on the effects of SCFA.

RESULTS

A SCFA mixture (75 mM acetate, 35 mM propionate and 20 mM butyrate) or individual SCFAs (130 mM) increased the mucus release into the colon in a similar manner. The individual SCFAs, but not lactate or succinate, stimulated colonic mucus secretion in similar concentration-dependent manners. Butyrate stimulated colonic mucus secretion at 20 mM, but acetate, propionate, lactate and succinate at this concentration did not. Pretreatment with an anti-cholinergic agent diminished the stimulatory effects of SCFAs on mucus secretion.

CONCLUSIONS

Lumen SCFAs, but not lactate or succinate, stimulate mucus release from the rat colon via a cholinergic nerve mechanism.

Experimental study of antidiarrheal activity of Salicairine

Experimental antidiarrheal activity of a traditionally used medication, Salicairine, was demonstrated in comparison to loperamide by significant inhibition of castor oil-induced diarrhea in mice (increases in hard faeces/total faeces ratio of 38 and 54 and 5 and 54% with respect to controls, at 0.5 and 1 mL/kg and 1 and 2 mg/kg, respectively) and bisacodyl-induced increase in large intestine transit in rats (125 and 280 and 210% with respect to controls, at 0.4 and 2 mL/kg Salicairine and 5 mg/kg loperamide, respectively). Salicairine was able to reduce contractions of isolated rat duodenum induced by barium chloride and acetylcholine, although not completely (that is about 60%) as seen with loperamide. Also, it did not change normal gastrointestinal transit in mice at doses of 0.5 to 1 mL/kg, conversely to loperamide which had a significant effect (decrease of 50%) at 2 mg/kg. Finally, Salicairine at 0.01 mL/mL, like loperamide at 0.2 mg/mL, significantly increased net fluid absorption in rat colon, either in basal conditions (30 and 64% respectively) or after a prostaglandin E1-induced increase in net fluid secretion (41 and 35%, respectively). The antidiarrheal activity of Salicairine is possibly related, at least in part, to an increase in colon net fluid absorption or a decrease in net fluid secretion.

Prostaglandin E2-mediated stimulation of mucus synthesis and secretion by rhein anthrone, the active metabolite of sennosides A and B, in the mouse colon

Rhein anthrone, the active metabolite of sennosides A and B, stimulated PGE2 release into the mouse colonic lumen. At 6.24 mg kg-1, it decreased net water and Na+ absorption significantly in the case of water, but could not reverse the net absorption in mouse ligated colon, although it enhanced net K+ secretion. Pretreatment with indomethacin diminished the effects of rhein anthrone except on K+ net secretion. Rhein anthrone or PGE2 markedly stimulated mucus secretion and synthesis in mouse ligated colon. The enhanced mucus secretion and synthesis induced by rhein anthrone were significantly suppressed by pretreatment with indomethacin. Our results have shown that the colonic secretion of water and electrolytes mediated by PGE2 is partly involved in the rhein anthrone-induced diarrhoea but that in mice, the mucoid diarrhoea induced by rhein anthrone results mainly from PGE2-mediated mucus synthesis and secretion in the colon.

Inhibition by loperamide of mucus secretion in the rat colon in vivo

The effect of loperamide on mucus secretion and the net transport of fluid, sodium and potassium was investigated in the perfused rat colon in vivo. Prostaglandin E2 (PGE2, 1 mg/kg per h intraarterially) and deoxycholic acid (2 mM intraluminally) were used as secretagogues. Mucus secretion was determined as the total amount of protein-bound hexose in the effluent. Under basal conditions, loperamide (6 mg/kg subcutaneously) slightly decreased mucus secretion and increased the absorption of fluid and sodium. PGE2 and deoxycholic acid stimulated mucus secretion about 4- and 9-fold, respectively. Loperamide abolished the mucus secretory response to PGE2 and reduced the response to deoxycholic acid by 50%. It also reduced the fluid secretion following PGE2 but did not affect the diminished fluid absorption following deoxycholic acid. Potassium secretion was not significantly influenced by loperamide and therefore was independent of the secretion of mucus. The data suggest that loperamide is a potent inhibitor of colonic mucus secretion, a property that possibly contributes to the antidiarrheal effect of this opiate analogue.

Influence of vasoactive intestinal peptide, secretin, and Ala4, Val5-secretin on the net movements of electrolytes, fluid, and mucus in the rat colon in vivo

The effect of vasoactive intestinal peptide (VIP), secretin, and VIP-secretin (Ala4, Val5-secretin) on the net movements of sodium, potassium, fluid, and mucus was investigated in the rat colon perfused in vivo. Peptides (1-100 micrograms/kg.h) were infused intra-arterially. VIP influenced electrolyte and fluid movements at a threshold dose 10- to 100-fold lower than secretin, whereas the secretory efficacy was not significantly different. Replacing the NH2-terminal hexapeptide of secretin by that of VIP did not markedly alter the effect of secretin. Mucus output was stimulated weakly by all three peptides. The results indicate that the larger colonic secretory activity of VIP as compared to secretin is not primarily due to the difference in their NH2-terminal sequence but probably requires the intact molecule.