Adrenoceptors in the human foetal small intestine

Improved use of the [13C]octanoic acid breath test as intra-individual parameter to study the effect of a prokinetic drug on gastric emptying in preterm infants with oral feeding intolerance

The [13C]octanoic acid breath test was used for the measurement of differences in gastric emptying in preterm infants for the evaluation of pharmacological therapy. In order to perform a good intra-individual comparison of the gastric emptying in preterm infants under non-standardisable test conditions, we adjusted t1/2 for variations in non-recovered label (=label retention) and introduced an "effective half 13CO2 breath excretion time" t1/2eff = t1/2/m expressed as min per percentage of the cumulative dose recovered. In a pilot study, we investigated the action of the gastrointestinal prokinetic drug cisapride on gastric emptying in seven premature infants, of whom four suffered from gastric stasis and three had constipation. The postnatal age and weight at the start of treatment ranged from 15 to 64 days and from 815 to 1635 g, respectively. All infants received the standard formula for premature infants (Nenatal, Nutricia). Cisapride was administered orally 0.2 mg/kg, four times daily. The changes in gastrointestinal motility were studied using the total bowel transit time of carmine red. After 7 days of treatment in all children, the gastric emptying coefficient and the half 13CO2 breath excretion time adjusted for label retention were improved (n=7, the gastric emptying coefficient range before treatment was 1.69-3.34 (mean 2.59 +/- 0.80) and after treatment it was 2.79-3.76 (mean 3.28 +/- 0.30); the half 13CO2 breath excretion time adjusted for label retention range before treatment was 3.0-14.7 min/% dose (mean 7.0 +/- 5.0) and after treatment 2.6-4.0 min/% dose (mean 3.1 +/- 0.6). The total bowel transit time was only slightly improved in two patients (n=7, mean total bowel transit time before: 23.7 h compared to mean total bowel transit time after 7 days of treatment: 35.5 h). Side effects during cisapride treatment were not seen. We conclude that in premature infants cisapride is effective in shortening gastric emptying time and reducing gastric stasis; the therapeutic role in constipation has to be further investigated.

Temporal changes in gastric volume in the human fetus in late pregnancy

Disturbed fetal gastrointestinal tract function is associated with hydramnios and may be a marker of later gastrointestinal disease. We investigated gastric motor function in the human fetus to establish the range and rate of fluctuation of gastric volume. Two pairs of orthogonal gastric diameters were measured at 5-min intervals for 1-h periods using a linear-array ultrasound scanner in 12 fetuses in late pregnancy (26-40, median 35.5 weeks gestation). A gastric volume index (GVI) was calculated. Maximum absolute gastric volume index correlated significantly with gestational age. The minimum gastric volume index as a percentage of the maximum (0-60.4%, median 28.1%) showed that marked changes in gastric dimensions occur. Filling (41.5-74.1, median 62.6 degrees) and emptying (46.6-80.9, median 61.7 degrees angles were calculated for the longest continuous filling and emptying periods using a linear model, and showed no difference in the rates of filling and emptying. Peak-to-peak and trough-to-trough durations suggested a periodicity of 35-55 min. Investigation of the development of normal fetal gastric motor activity may lead to a better understanding of postnatal adjustment to enteral feeding, and may provide a diagnostic method for antenatal diagnosis of gastrointestinal functional disturbances.

Collagen production by human smooth muscle cells isolated during intestinal organogenesis

The extracellular matrix influences organogenesis by modulating cell behavior. In humans, collagen is the major matrix constituent of the adult intestinal wall and is synthesized by smooth muscle cells. The objective of the current study was to examine collagen production by fetal human intestinal smooth muscle cells isolated during intestinal morphogenesis. Techniques were developed for the isolation and culture of human fetal intestinal smooth muscle cells. The cultured cells were confirmed as muscle by immunohistochemical stains for cytoskeletal filaments and documentation of contractile behavior. In culture, these cells stained for mesenchymal and muscle cytoskeletal proteins: vimentin, actin, and desmin, and did not stain for neural or epithelial markers. The muscle cells contracted in response to acetylcholine, in contrast to human fetal dermal fibroblasts which did not contract appreciably. Collagen production was assayed by the uptake of [3H]-proline into collagenase-digestible protein. Collagen production was greatest at 11 weeks gestation, the youngest age studied. By 20 weeks gestation, collagen production had decreased to adult levels. However, when compared to another matrix-producing fetal mesenchymal cell, the dermal fibroblast, intestinal smooth muscle cells produced twice as much collagen. Collagen types were determined by polyacrylamide slab gel electrophoresis. Smooth muscle cells predominantly produced types I and III collagen alpha chains. Therefore, collagen production is a significant function of human fetal intestinal smooth muscle cells, and probably plays a major role in the development of intestinal structure. The in vitro model presented here provides a means of studying the regulation of this collagen production throughout intestinal organogenesis.

Developmental disappearance of excitatory alpha 1-adrenoceptor function in the oesophagus of chick embryo

1. Developmental change in the response to noradrenaline (NA) and 5-hydroxytryptamine (5-HT) was investigated in the chick oesophagus between 9 and 21 days of incubation and 4 days after hatching. 2. NA (5 microM) produced a significant contraction in the oesophagus at 9 days of incubation. The NA-induced contraction progressively decreased with development and changed to an inhibition of spontaneous contraction or a small relaxation by 17 days of incubation. 3. The NA-induced contractile response was inhibited by phentolamine (2.7 microM) and prazosin (0.55 microM). Phenylephrine (5 microM) but not clonidine (5-50 microM), also induced a contraction at early stages. The relaxation response to NA was sensitive to the beta-receptor blocker, carteolol (3.4 microM). 4. Pretreatment with carteolol unmasked the contractile responses to NA in preparations at 17-19 days of incubation. However, even in the presence of carteolol, the contraction produced by NA decreased and disappeared by the time of hatching. This change in response to NA is accompanied by a decline in the pD2 value. The response to phenylephrine (5 microM) followed the same pattern as that to NA. 5. The maximum binding sites of [3H]-dihydroergocryptine to the crude membrane preparation from oesophagus changed little at 13, 17 and 21 days of incubation. 6. Isoprenaline (Iso, 0.01-20 microM) caused a carteolol-sensitive relaxation in the carbachol-contracted oesophagus after 13 days of incubation. The sensitivity (pD2 value) to Iso decreased slightly up to 17 days of incubation. 7. 5-HT (10 microM) caused a contraction in the oesophagus after 13 days of incubation and the amplitudem of the response increased up to 17 days of incubation. The response to 5-HT was abolished by methysergide (1 microM) but not by tetrodotoxin (0.78 microM) or atropine (1 microM) at every stage tested. 8. These results suggest that the response to NA changed from an alpha-adrenoceptor-mediated contraction to a beta-receptor-mediated relaxation during the embryonic period, resulting partly from the decline and disappearance of excitatory alpha-receptor function in the chick oesophagus.

Postnatal development of responsiveness to adrenergic agents of longitudinal and circular smooth muscles from cat terminal ileum

The changes in the responsiveness of the isolated longitudinal and circular smooth muscles from cat terminal ileum to adrenergic agents during the postnatal period were studied by the effect of noradrenaline (0.01-100 mumol) on the smooth muscle tone and phasic contractions. Cumulatively applied noradrenaline (0.01-10 mumol) decreased the longitudinal muscle tone without age-dependent differences via inhibitory alpha 1-adrenoceptors. Noradrenaline decreased the phasic contraction amplitude of longitudinal muscle via inhibitory alpha 1-adrenoceptors. Cumulatively applied noradrenaline (0.01-10 mumol) exerted an age-dependent effect on the circular muscle tone via stimulatory alpha 1-adrenoceptors. alpha 1-adrenoceptors continue to develop functionally at 60 days postnatal. Noradrenaline decreased the phasic contraction amplitude of the circular muscle and exerted a stimulant effect on the tone which suggested an existence of two alpha 1-adrenoceptor subtypes.

Beta-adrenergic blockade and the gastrointestinal system

As beta-adrenergic blockers grow increasingly popular for the therapy of a wide variety of disorders, it becomes increasingly important to appreciate the spectrum of physiologic effects on the gastrointestinal system and the potential hazards associated with use of these agents. This review details the effects of the beta-adrenergic blocking agents on the gastrointestinal tract.

The actions of prostaglandins E2 and F2alpha on human foetal intestine

Human foetal small and large intestine responded to prostaglandins E(2) and F(2alpha), the gestational age of the tissue being between 14 and 26 weeks. The predominant response to both prostaglandins was a contraction of each region of the intestine studied. The response to both prostaglandins was antagonized selectively by poly.phloretin phosphate.