Intraluminal Fluid Accumulation Research Articles

A Synthetic Peptide Corresponding to Amino Acid Residues 34 to 37 of Human Follicle-Stimulating Hormone -Subunit Accelerates the Onset of Puberty in Male and Female Mice

We have previously reported that a synthetic peptide amide corresponding to residues 34–37 (TRDL, threonine, arginine-aspartic acid-leucine) of the β-subunit of human FSH induced prolonged vaginal estrus in normally cycling female mice (see Ref. 15). These results represented the first demonstration of an in vivo effect of a gonadotropin-related synthetic peptide on reproductive processes. We have extended these studies to examine possible effects of TRDL on the onset of puberty in female mice. In two replicated experiments, vehicle-injected control mice attained first vaginal estrus by day 39. An ip injection of 200 ug TRDL/g BW to 28-day-old prepubertal female mice, however, accelerated the onset of first vaginal estrus by 7 days in 11 of 12 (11/12) (Exp 1) and 7/9 (Exp 2) mice. Serum estradiol levels were significantly (P = 0.017) elevated in TRDL-treated mice, whereas progesterone was unchanged. Uteri of TRDL-treated mice were significantly (P = 0.003) heavier than uteri of vehicle-injected control animals of the same age and body weight. Intraluminal fluid accumulation (ballooning) at proestrus was absent in 20/21 TRDL-treated females, as were oviductal ova and ovarian corpora lutea. These phenomena are characteristic of the first estrous cycles of female mice isolated from males. To obtain further evidence for in vivo effects of TRDL, we assessed the ability of TRDL to accelerate the onset of puberty in male mice. When given as five consecutive daily ip injections of 200 ug/g BW to 28-day-old prepubertal male mice, TRDL significantly increased testis weight, when compared with vehicle-injected control mice of the same age and BW (171.3 ± 3.8 mg vs. 151.6 ± 4.3 mg, P = 0.001) and induced a 6.5-fold increase in serum testosterone levels. These studies confirm the previously reported in vivo activity of a synthetic peptide corresponding to human FSH-β subunit 34–37 (TRDL) in adult female mice and extend its effects to the acceleration of the onset of puberty in immature male and female mice.

Reactive oxygen and nitrogen metabolites as mediators of secretory diarrhea

S ecretory diarrhea is a common symptom associated with inflammation of the intestinal mucosa, regardless of the factor(s) responsible for initiation of the inflammation.* Reactive metabolites of oxygen and nitrogen, through oxidation and free radical reactions, are believed to contribute to the diarrhea by acting as secretagogues. 2 The purpose of this report is to succinctly review the evidence in support of the probability that highly reactive oxygenand nitrogen-containing molecules produced in the inflamed intestinal mucosa contribute to secretory diarrhea. Patients with ulcerative colitis can have fecal excretion weights of 234 to as much as 1500 g/day, 3-5 thus exceeding values that define diarrhea clinically. Harris and Shields 6 and Head et al. v reported that the colon of patients with proctocolitis and Crohn's disease, respectively, absorbed water and electrolytes at a reduced rate compared with healthy subjects. Similar findings were noted by other investigators in studies in vivo *-n and in vitro. 12'13 Impaired fluid absorption in the jejunum occurs in patients with ulcerative colitis, .4 and the coIonic mucosa from infants with colitis secretes NaC1 when studied in vitro. ~5 It is not possible from studies in patients with inflammatory bowel disease (IBD) to define with certainty the cause of the intraluminal fluid accumulation. There is little compelling evidence from human studies that active electrolyte secretion, rather than inhibition of absorption in the small bowel or colon, causes the diarrhea.16 The apparent reduction of sodium absorption may be due to electrolyte movement from the blood to the lumen. Studies in vivo, using 22Na and 36C1 or other suitable radiolabeled solutes, have not been performed in patients to confirm a mechanism of serosal-to-mucosal transport (i.e., active secretion). Activation of a secretory flux has been inferred, mostly from in vitro short-circuit current studies in which inflammatory mediators evoke secretion in normal mucosa. ~7'~8 However, in inflamed mucosa, the secretory response is less vigorous than in healthy tissue. 19 Thus, additional factors, such as increased mucosal permeability 2a6'2°-23 and interference with Na+,K+-adenosine triphosphatase and epithelial cell absorptive processes, 24 probably contribute to luminal fluid accumulation in IBD. As for potential secretagogues, a plethora of candidates is possible, including neuropeptides, 25 kinins, 26 C5a, 27'28 platelet activating factor, 29 biogenic amines, cytokines, eicosanoids, and reactive metabolites of oxygen and nitrogen. ~8'3°'31 Other inflammatory conditions of the gut are also associated with secretory diarrhea. For example, patients with food allergy often present with diarrhea, presumed to be primarily caused by intestinal secretion. 3° The mucosal response is associated with an eosinophilic enteritis. 3°'32 Rodent models have been developed based on immediate hypersensitivity reactions. 33 On challenge, sensitized animals show a mucosal inflammatory response characterized by increased permeability, 34 inhibition of electrolyte absorption, or stimulation of secretion. 3°'35-3v It is unlikely that a single mediator is responsible for these effects. There are a variety of factors associated with induction of an immune response by the intestinal mucosa. Most obvious among these are enteric infections. Salmonella, Shigella, and Escherichia coli (O157:H7) infections are especially associated with mucosal inflammation and secretory diarrhea. 38 E. coil O157:H7 reduces sodium absorption and stimulates secretion of chloride ions in the distal colon of rabbits, and these effects are related to infiltration of the tissue by neutrophils. 39 The parasite Trichinella spiralis also initiates an inflammatory response in the mucosa, which has been well characterized and serves as a model for investigating immune-mediated intestinal secretion in rats. 37 In rabbits infected with Yersinia entercolitica, inhibition of short-chain fatty acid absorption due to reduced Na + uptake (Na+/H + exchange) was sug-

Formula omitted] methyl ester modulates intestinal secretion and motility produced by carbachol

The effects of the nitric oxide (NO) synthesis inhibitor, N G - nitro- L-arginine methyl ester, on carbachol-induced diarrhoea, fluid accumulation and motility changes were studied. Pretreatment of mice with N G - nitro- L-arginine methyl ester (1–25 mg/kg i.p.) and N G - nitro- L-arginine (2.5–50 mg/kg i.p.) butt not N G - nitro- D-arginine methyl ester (25 mg/kg i.p.) prevented in a dose-related manner the carbachol (0.5 mg/kg i.p.)-induced diarrhoea in mice. L-Arginine (150–1500 mg/kg i.p.) administered to mice pretreated with N G - nitro- L-arginine methyl ester counteracted the antidiarrhoeal activity of N G - nitro- L-arginine methyl ester in a dose-related manner. Pretreatment of rats with N G - nitro- L-arginine methyl ester (2.5–25 mg/kg i.p.) decreased the intestinal fluid accumulation induced by carbachol in rats. N G - Nitro- D-arginine methyl ester was without effect. Intraperitoneal pretreatment of rats with N G - nitro- L-arginine methyl ester (2.5–25 mg/kg) reduced the increase in small intestinal transit induced by carbachol. N G - nitro- L-arginine methyl ester had no effect. These results provide evidence that nitric oxide may play a role in diarrhoea, intraluminal fluid accumulation and motility changes induced by carbachol.

Effects of quercetin on the gastrointestinal tract in rats and mice

AbstractIntraperitoneal administration of quercetin (6.25–50 mg/kg) significantly (p<0.5‐0.01) reduced intestinal transit in mice and this effect was antagonized by yohimbine and phentolamine but not by atropine or naloxone. Quercetin (12.5–50 mg/kg) reduced also (p<0.05‐0.01) intraluminal accumulation of fluid and diarrhoea induced by castor oil and these effects were antagonized by yohimbine. Finally quercetin (12.5–50 mg/kg) reduced the area of gastric ulcer but not the number. It is suggested that α2‐adrenergic receptors mediate the effect of quercetin on intestinal motility and secretion.

Stereospecific actions of misoprostol on rat colonic electrolyte transport

Misoprostol (Miso) produces a mild, transient diarrhea in some patients, which is believed to be partly due to intraluminal fluid accumulation. To better understand this diarrheagenic action, we compared the effects of Miso, its 4 stereoisomers (11R16R, 11R16S, 11S16S, 11S16R), misoprostol free acid (Miso-FA), and 16,16-dimethyl PGE 2 (dmPGE 2) on rat colonic electrolyte transport in vitro. Increases in short-circuit current (lsc) were measured (after serosal addition) in segments of mucosa stripped of muscularis and mounted in Ussing chambers. The rank order of apparent potencies, in terms of threshold, were ( μM): 11 R, 16S (1.2) ≈ dmPGE 2 (1.0)> Miso-FA (10.0) ∼ Miso ⪢ 11R, 16R; 11S, 16R; 11S, 16S (all inactive at 100 μM). The response to dmPGE 2 and Miso was attenuated in the presence of the Na+/K+/Cl − co-transport inhibitor bumetanide (100 μM). Pretreatment with atropine (0.1 μM) did not affect the lsc response to Miso, Miso-FA, or dmPGE 2. Tetrodotoxin partially attenuated (39±9% inhibition) the response to Miso-FA, but did not affect Miso or dmPGE 2. In conclusion, Miso increases Cl − secretion across rat colonic mucosa through a direct action on epithelial cells. The activity resides in the 11R, 16S isomer, thus implying a stereospecific interaction at PGE receptors. The effect of Miso to stimulate epithelial Cl − secretion might contribute to its diarrheagenic action in vivo.

Laxatives: clinical pharmacology and rational use.

Proprietary laxatives represent a multimillion dollar industry and are widely used by the apparently well population. They are traditionally classified into bulk laxatives, lubricants, stimulants, stool softeners, and osmotic laxatives. The latter 3 probably act mainly by favouring accumulation of fluids and electrolytes in the lumen of the gut. Magnesium-containing saline laxatives are believed to act by releasing cholecystokinin which, in turn, favours intraluminal fluid accumulation. Bran is not a proprietary laxative. It is a bulking agent with capacity to hold water in the stool, thereby improving bowel function. The lubricant, mineral oil (liquid paraffin), is obsolete.

Measurement of Serum Steroid and Gonadotropin Levels and Uterine and Ovarian Variables throughout 4 Day and 5 Day Estrous Cycles in the Rat1

The present study was undertaken to characterize hormonal and morphological events in 4 day and 5 day rat cycles, in order to test 3 different theories concerning the etiological factors altering follicular phase length in mammals. Three rats were killed at each 2 h interval throughout each cycle type. In addition to organ weight measurements, serum levels of estradiol, progesterone, 20α-hydroxypreg-4-en-3-one, LH, FSH and prolactin were assessed in terminal samples. The beginning of uterine intraluminal fluid accumulation coincided with the decline in progesterone levels seen during diestrus, rather than with the rise in estrogen and was delayed 12 h in the 5 day cycle from the time of last estrus. The retention of this fluid during the evening of proestrus was 6 h longer in the 4 day cycling rat. Ovulation occurred earlier in the 5 day cycling rats than in those with a 4 day cycle. No significant differences in the gonadotropins or 20α-hydroxypreg-4-en-3-one were seen when comparing the 2 types of cycles. Estradiol rose during the night of diestrus I (the same time in the cycle) and was identical in both cycle types. Progesterone was not released on proestrus prior to the LH surge in either type of cycle. However, we did find that progesterone values were higher for a longer period of time throughout diestrus I in 5 day cycles. These data have led us to conclude that the 5 day cycle is due to a prolonged progesterone secretion during the metestrous and diestrous stages of the cycle.

Perfusion of Rabbit Colon with Ricinoleic Acid: Dose-Related Mucosal Injury, Fluid Secretion, and Increased Permeability

Morphology of the rabbit colon was examined by light and scanning electron microscopy after perfusion of the organ with 2.5, 5.0, 7.5, and 10 mM sodium ricinoleate. Colons perfused with control buffer showed the expected normal appearances, whereas ricinoleate produced desquamation of surface epithelial cells. Surface changes in the colon were comparable with those reported after similar treatment of the rabbit ileum. Concomitant with these histological changes was loss of DNA into the lumen of the colon. Dose-related changes in net fluid transport and mucosal permeability (as assessed by lumen to plasma flux of low molecular weight polyethylene glycols and plasma to lumen flux of urea and creatinine) were also associated with ricinoleate perfusion. These structural and functional alterations may contribute to intraluminal accumulation of fluid and catharsis that can result from administration of ricinoleic acid (castor oil). The findings might also pertain to the pathophysiology of steatorrheal diseases, because dietary fatty acids of similar chemical structure are known to have comparable effects on the intestinal mucosa.

The Syrian hamster: a reproducible model for studying changes in intestinal fluid secretion in response to enterotoxin challenge

Syrian hamsters respond in a predictable and reproducible manner to intragastric administration of purified cholera enterotoxin by intraluminal accumulation of fluid in the small bowel, cecum, and proximal colon. In the majority of animals this process is self limiting, and recovery occurs with full reabsorption of intestinal fluid by 30 to 35 h. The secretory response to 75 mug of cholera toxin has been defined, and the model was utilized to study the inhibitory effects of indomethacin, polymyxin B sulfate, glucose electrolyte solutions, and colchicine. These studies demonstrate its potential usefulness as a convenient and inexpensive technique for evaluation of pharmacological agents that might inhibit intestinal fluid secretion.

The effects of distention and obstruction on the accumulation of fluid in the lumen of small bowel of dogs.

Fluid accumulation in either the obstructed upper or lower intestinal segments of the dog was found in most animals to be negligible. Distention pressures of 25 cm of water tended to reduce fluid accumulation within the intestinal lumen. These studies suggest that if the dog is comparable to man, the intraluminal accumulation of fluid in the obstructed small bowel of man might be due to alterations in blood supply to the intestine, rather than to obstruction per se, or the accumulated fluid originates proximal to the jejunum.