Acute hypervolaemia increases gastroduodenal resistance to the flow of liquid in the rat.

We have observed that acute blood volume expansion increases the gastroduodenal resistance to the flow of liquid in anesthetized dogs, while retraction decreases it (Santos et al. (1991) Acta Physiologica Scandinavica, 143: 261-269). This study evaluates the effect of blood volume expansion and retraction on the gastric emptying of liquid in awake rats using a modification of the technique of Scarpignato (1980) (Archives Internationales de Pharmacodynamie et de Therapie,. Male Wistar rats (180-200 g) were fasted for 16 h with water ad libitum and 1.5 ml of the test meal (0.5 mg/ml phenol red solution in 5% glucose) was delivered to the stomach immediately after random submission to one of the following protocols: 1) normovolemic control (N = 22), 2) expansion (N = 72) by intravenous infusion (1 ml/min) of Ringer-bicarbonate solution, volumes of 1, 2, 3 or 5% body weight, or 3) retraction (N = 22) by controlled bleeding (1.5 ml/100 g). Gastric emptying of liquid was inhibited by 19-51.2% (P<0.05) after blood volume expansion (volumes of 1, 2, 3 or 5% body weight). Blood volume expansion produced a sustained increase in central venous pressure while mean arterial pressure was transiently increased during expansion (P<0.05). Blood volume retraction increased gastric emptying by 28.5-49.9% (P<0.05) and decreased central venous pressure and mean arterial pressure (P<0.05). Infusion of the shed blood 10 min after bleeding reversed the effect of retraction on gastric emptying. These findings suggest that gastric emptying of liquid is subject to modulation by the blood volume.

Section: Discussionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 97%

Variations in gastric emptying of liquid elicited by acute blood volume changes in awake rats

Gondim

Oliveira

Graça

et al. 1998

“…Gastrointestinal motor and absorptive functions and extracellular fluid volume are tightly interlinked, and changes in blood volume may accordingly modify gastroduodenal flow (15,16). Experimental hypervolemia decreases gastroduodenal flow, whereas experimental hypovolemia has the opposite effect (15,16).…”

mentioning

confidence: 99%

Effects of adrenalectomy and adrenal enucleation on liquid gastric emptying in rats

Ronsini

Collares

2000

The effects of adrenalectomy and adrenal enucleation on liquid gastric emptying were studied in male Wistar rats that were adrenalectomized, adrenal enucleated (AE) or sham operated (SH). The animals in the first group had free access to a 1% NaCl solution (ADS), while the animals in the second and third groups were divided into two subgroups, which ingested either tap water (AEW, SHW) or 1% NaCl solution (AES, SHS). The gastric emptying study was performed on the 16th post-operative day. Three test meals labeled with phenol red (6 mg/dl) were used (0.9% NaCl, 1.8% NaCl and 5% glucose). Percent gastric retention was determined 10 min after orogastric infusion of the NaCl test meals and 15 min after the glucose meal. Gastric retention of the ADS subgroup was significantly lower (P<0.01) (median = 19.8% vs 25.5% for SHW, vs 31.9% for SHS, vs 25.7% for AEW, and vs 27.1% for AES) for the 0.9% NaCl test meal and for the 1.8% NaCl test meal (33.5% for ADS vs 47.5% for AEW and 50.6% for AES). When 5% glucose was used as a test meal, gastric retention was similar for all subgroups. These results suggest that ablation of the adrenal cortex results in increased gastric emptying of an isosmolar NaCl meal. Key wordsAdrenal hormone insufficiency or adrenalectomy is known to affect certain gastrointestinal tract functions (1,2). However, the role of these hormones in the regulation of gastric emptying is unclear. This study was therefore designed to examine the effects of adrenalectomy and adrenal enucleation on liquid gastric emptying (GE) in rats.Male Wistar rats aged 8 weeks (195-240 g) were used after four days of acclimatization to the laboratory (25 ± 3 o C and 12-h light/dark cycle). For the experiments, the rats were adrenalectomized (AD), adrenal enucleated (AE) or sham operated (SH).Under general ethyl ether anesthesia, the retroperitoneal cavity was opened on both sides to expose the adrenal glands, which were then entirely removed (AD group) or partially removed (AE group). In the latter case, the adrenal medulla was removed by slitting the adrenal capsule and gently squeezing out this portion, leaving the remaining adrenocortical tissue in place. In the rats of the SH group, the glands were isolated as described above but were left intact. The rats were housed in individual cages for at least one week after surgery.Rats of the AD group were housed with

“…We have observed that acute BV changes modify the GI motility in anesthetized rats and dogs: gastric and jejunal compliance (9,10), as well as the resistance offered by the gastroduodenal segment to the flow of liquid (11,12). We have also recently extended these observations to the ileocolonic region (15).…”

Section: Discussionmentioning

confidence: 98%

“…In a barostatically perfused system we have also observed, in anesthetized dogs and rats, that the resistance offered by the gastroduodenal (GD) segment to the flow of liquid is modulated by BV levels: BV expansion decreased the GD flow while BV retraction increased it (11,12).…”

Section: Introductionmentioning

confidence: 93%

Acute blood volume expansion delays the gastrointestinal transit of a charcoal meal in awake rats

Graça

et al. 1998

The present study evaluates the effect of blood volume expansion on the gastrointestinal transit of a charchoal meal (2.5 ml of an aqueous suspension consisting of 5% charcoal and 5% gum arabic) in awake male Wistar rats (200-270 g). On the day before the experiments, the rats were anesthetized with ether, submitted to left jugular vein cannulation and fasted with water ad libitum until 2 h before the gastrointestinal transit measurement. Blood volume expansion by iv infusion of 1 ml/min Ringer bicarbonate in volumes of 3, 4 or 5% body weight delayed gastrointestinal transit at 10 min after test meal administration by 21.3-26.7% (P<0.05), but no effect was observed after 1 or 2% body weight expansion. The effect of blood volume expansion (up to 5% body weight) on gastrointestinal transit lasted for at least 60 min (P<0.05). Mean arterial pressure increased transiently and central venous pressure increased and hematocrit decreased (P<0.05). Subdiaphragmatic vagotomy and yohimbine (3 mg/kg) prevented the delay caused by expansion on gastrointestinal transit, while atropine (0.5 mg/kg), L-NAME (2 mg/kg), hexamethonium (10 mg/kg), prazosin (1 mg/kg) or propranolol (2 mg/kg) were ineffective. These data show that blood volume expansion delays the gastrointestinal transit of a charcoal meal and that vagal and yohimbine-sensitive pathways appear to be involved in this phenomenon. The delay in gastrointestinal transit observed here, taken together with the modifications of gastrointestinal permeability to salt and water reported by others, may be part of the mechanisms involved in liquid excess management.