Electrogenic glucose absorption in untreated and treated coeliac disease.

Abstract

SUMMARY Using a method for measuring changes in transmural potential difference across the human jejunum in vivo, the operational kinetic parameters of 'Apparent Km' and PD max for the active electrogenic component of glucose absorption were estimated in a group of healthy volunteers and in patients with coeliac disease. Both the 'Apparent Km' (17 2 mM; mean SEM) and the PD max (8.6 ± 0 7 mV) in nine patients with untreated coeliac disease were significantly lower (p < 0 005) than in the control group ('Apparent Km' = 74 ± 5 mM; PD max 12-8 ± 0-9 mV, n = 20). Treatment of five coeliac patients by gluten withdrawal for less than three months increased significantly the values of both the 'Apparent Km' (35 ± 6 mM) and the PD max (1li4 ± 1-2 mV). Treatment of five patients for more than six months caused a further increase in the values of both kinetic parameters ('Apparent Km' = 108 ± 13 mM; PD max = 15-6 ± 2-7 mV) to levels which exceeded those in healthy subjects. The possible interpretations of the differences in the kinetic characteristics of electrogenic glucose transport between coeliac patients and healthy subjects are discussed.

In vivo recording of the glucose- and disaccharide-evoked potentials from the human jejunum in infancy

“…Read et al [18] reported the values for Kt in normal adults of 36 + 6 mM in rive, while Sacher et al [19] reported a value of 5.5 mM in adults in vivo. On the other hand, the values of APDG max in the present study were almost identical to those reported by others [15][16][17][18][19]23]. The difference in the values of Kt seems not to be due to the difference in the true affinity of sugars at the transport site but to the difference of infusion method and/or the difference in the unstirred layer in the intestinal lumen.…”

“…In addition to these in vitro experiments, changes in the transmural potential difference in vivo in both animal and human jejunum have been reported in association with intake or infusion of sugars [5,6,[15][16][17][18][19]23].…”

Unstirred layer and kinetics of electrogenic glucose absorption in the human jejunum in situ

“…The PDmax in the active coeliac group (6f8 + 0 7 mV) was lower than in controls (7-6 + 0-6 mV) but not significantly so, while the PDmax in the treated coeliac group (10-6 + 0 9 mV) was significantly higher than in both the active coeliac and control groups. It should be noted that both operational kinetic parameters obtained in the present study are much lower than those obtained previously (Read et al, 1976b) because of the use of siphonage. Analysis of the results using a computer simulation indicates that the reduction in Apparent Km in active coeliac disease can be caused by the interaction of the decreased maximal absorption rate for glucose (Jmax) with the attenuated unstirred layer.…”

“…Thus, pooling of successive solutions in the jejunum was minimised, allowing rapid change from one solution to the next; (2) intraluminal pressure was measured at the infusion site by means of a transducer (Bell and Howell, model 4-327 L221) connected to the side arm of the infusion column. This allowed us to check that intestinal motility, suppressed by propantheline bromide (Read et al, 1974(Read et al, , 1976bBrown et al, 1976), remained quiescent during the recording period; (3) both the pressure and the PD signals passed through electronic filters with fivesecond time constants to suppress fluctuations in the record caused by the infusion pump, respiration, electrocardiogram, intestinal myoelectric activity, and 50 Hz mains interference.…”

“…Using this technique we observed that the operational kinetic parameters ('Apparent Km', PDmax) for the active electrogenic component of glucose absorption were significantly lower in untreated coeliac disease than in healthy controls (Read et al, 1976b). It is possible that these results could be caused by differences in the thickness of the layer of unstirred fluid which lies adjacent to the mucosal epithelium.…”