Effect of metoclopramide on gastric liquid emptying in patients with diabetic gastroparesis.

Metoclopramide tablets have been approved for use in the acute and chronic management of diabetic gastroparesis. Its efficacy as an antiemetic has been well documented. We measured the acute and chronic effects of oral metoclopramide on gastric liquid emptying in 12 diabetic patients with symptoms of stasis using scintiscanning techniques. We found that liquid emptying in these subjects was abnormal, as determined by residue area determination when compared to normal volunteers (P less than 0.01). Metoclopramide 10 mg orally acutely enhanced emptying, restoring it to control values (P less than 0.01). In contrast, when gastric emptying was evaluated following one month of chronic liquid metoclopramide use, 10 mg before each meal, the acute effect of the drug on emptying could no longer be demonstrated and residue areas returned to baseline values, suggesting that chronic oral administration of metoclopramide may result in a loss of the gastrokinetic properties of this drug.

Characterization and quantitation of human hepatic estrogen receptor.

Because the liver is an estrogen-sensitive organ and such sensitivity necessitates the presence of an hepatic estrogen receptor, we assayed whole human liver cytosol for the presence of estrogen receptor. Scatchard plot analysis of specific [3H]diethylstilbestrol binding to whole human liver cytosol from both sexes demonstrated hormone binding that is of high affinity (Kd = 10(-10)M) and low capacity (1-10 fmol/mg cytosol protein), and that is saturable and specific for steroidal and nonsteroidal estrogens, but not for other steroids. The protein can be further characterized as an estrogen receptor by its binding to heparin-Sepharose. In addition, gel filtration chromatography of [3H]estrogen-labeled cytosol on Sephadex G-100 indicates that potentially contaminating proteins, such as albumin and sex-steroid-binding globulin, do not bind [3H]estrogen in whole cytosol. We conclude that human liver from both sexes has estrogen receptor and that the presence of estrogen receptor in human liver explains the sensitivity of the human liver to estrogen.

Comparison of methods for analyzing gastric isotope emptying.

The gastric emptying of 99mTc-sulfur colloid, ingested in a nutrient liquid test meal, was followed by gamma camera for normals, diabetics, and diabetics receiving intravenous metoclopramide. Gastric emptying patterns of 99mTc by these groups present as normal, slow, and rapid on simple graphic inspection. Half times of indicator emptying were computed from inspection and from least-squares linear regressions of log(base e) residue versus time for the total postpeak curve and for the remainder of the 15-min postpeak curve. In addition, the percent of 99mTc residue leaving at, and the area under, the residue curve until 6, 12, 24, and 60 min postpeak and the indicator mean transit time (MTT) were computed. Standard half-time determinations revealed no significant differences among the three groups, despite obvious visual differences among them. In contrast, the mean transit time of the rapid group was significantly less than that of the slow (P less than 0.01) and normal (P less than 0.05) groups. However, no statistical difference was noted between the slow and the normal emptiers (P greater than 0.1) using the MTT measure. The percent of particles leaving the stomach and the area under the residue curves demonstrated significant differences among the three groups, reflecting the obvious visual perceptions gained from simple curve inspection. Because the percent of indicator particles leaving the stomach region at a given time reflects a single time, it was concluded that the residue area represents the most reliable, objective, and quantifiable parameter for testing of significant differences.

Validity of iodoantipyrine clearance for measuring gastrointestinal tissue blood flow.

Simultaneous determinations of 1) the clearance (mF) of 4-iodoantipyrine (IAP) and tritiated water, 2) the mF of IAP and total circulating tissue blood volume, 3) the mF of IAP and either 15- or 25-micrometers-diam-microsphere-measured flow, and 4) 15- and 25-micrometers-diam-microsphere-measured flow were made on tissues from dog gastrointestinal tracts. Results show the mF of IAP equals or exceeds that of tritiated water in all tissue layers, and tissue blood volume does not affect the measurement of the IAP mF. Perfusion of the gastrointestinal wall exhibits macroscopic heterogeneity due to differences in perfusion of the three tissue layers, but an effect of microscopic heterogeneity on tissue mF assessment was not apparent. Composite total-wall IAP mF was not significantly different from 25-micrometers-microsphere total-wall flow and was identical to this flow when colonic locations were omitted. Comparisons of 15-micrometers-microsphere flow to IAP mF and to 25-micrometers-microsphere flow both indicated shunting of 15-micrometers-microspheres. Such shunting occurred predominantly through submucosal and muscle layers. It is concluded that IAP clearance accurately measures blood flow in gastrointestinal tissue.

Response of transmural electrical parameters across in vitro everted sacs of hamster jejunum to variations in oxygenation rate.

1. The response of the electrical potential difference, short circuit current, and resistance across everted sacs of hamster jejunum to variations in the mucosal solution gassing rate was investigated. 2. Contrary to previous reports by others, it was found that the potential difference responds to increases in mucosal solution gassing rate by increasing in magnitude during the first 20 min of incubation. 3. The increases in potential difference were parallelled by increases in short circuit current but not by changes in resistance. 4. Increases in mucosal solution gassing rate increased epithelial cell O2 availability and this effect was determined to be due to increased stirring by gas bubbles. From the data, it was deduced that the minimum thickness of the mucosally located functional unstirred layer is between 0.08 and 0.16 cm when less than the full magnitude of electrical activity is observed across the everted sac preparation. 5. Serosal N2 or O2 had little or no effect on electrical parameters under maximum mucosal oxygenating conditions but dramatically affected these parameters when less than maximum mucosal oxygenating conditions were used. 6. Qualitative variations in the magnitude of the short circuit current across this preparation with respect to Cl- dependence were demonstrated. These variations were dependent upon the level of O2 availability, being apparent at high levels of O2 and absent at low levels. 7. It is concluded that the thickness of mucosally located unstirred layers can determine the O2 availability to the mucosa of everted sacs of hamster jejunum and thereby influence the observable magnitude and pattern of ionic dependence of the short circuit current across this preparation.

Sodium chloride transport by rabbit gallbladder. Direct evidence for a coupled NaCl influx process.

The results of the present study that NaCl transport by in vitro rabbit gallbladder must be a consequence of a neutral coupled carrier-mediated mechanism that ultimately results in the active absorption of both ions; pure electrical coupling between the movements of Na and Cl can be excluded on the grounds of electrphysiologic considerations. Studies on the unidirectional influxes of Na and Cl have localized the site of this coupled mechanism to the mucosal membranes. Studies on the intracellular ion concentrations and the intracellular electrical potential are consistent with the notion that (a) the coupled NaCl influx process results in the movement of Cl from the mucosal solution into the cell against an apparent electrochemical potential difference; (b) the energy for the uphill movement of Cl is derived from the Na gradient across the mucosal membrane which is maintained by an active Na extrusion mechanism located at the basolateral membranes; and (c) Cl exit from the cell across the basolateral membranes is directed down an electrochemical potential gradient and may be diffusional. Finally, as for the case of rabbit ileum, the coupled NaCl influx process is inhibited by elevated intracellular levels of cyclic 3',5'-adenosine monophosphate. A working model for transcellular and paracellular NaCl transport by in vitro rabbit gallbladder is proposed.

An analysis of the D-glucose influx kinetics of in vitro hamster jejunum, based on considerations of the mass-transfer coefficient.

1. A study designed specifically to investigate the effects of unstirred layers on the apparent glucose-influx kinetics of hamster jejunum was conducted. 2. The apparent V was 12.81, 10.71, 9.75, 10.17 and 9.33 mumol/cm-2 - h while the apparent Km was 7.42, 3.95, 1.87, 0.93 and 0.5 mM, respectively, when the rate of shaking the incubation flasks was 40, 80, 120, 160 and 200 cycles/min. 3. Extrapolation of the slope and reciprocal intercept of Lineweaver-Burke plots of the data to infinite shaking rate is mathematically justified to yield the slope and intercept of a Lineweaver-Burk plot which is uncomplicated by unstirred layers. These extrapolations were found to have a regression coefficient = 1 when plotted as (intercept)-1 or slope = b0 + b1b-(shake)-2 where b = 2.764 for the slope plot and 6.626 for the (intercept)-1 plot. From the values of b0 one obtains a Km of 0.41 and a V 0f 0.35 which should represent the true kinetic parameters for glucose influx into this tissue under the experimental conditions employed. 4. Values of the theoretical flux expected on a basis of unstirred-layer thickness which was calculated from the relation Cb (for J = V/2) = Km + 0.5 V/Kd agreed with the experimental values of J in some instances but the 95% confidence interval of the theoretical and experimental values did not overlap in many instances at low shaking rates and low concentrations of glucose. 5. A factor theta representing the error between the theoretical and experimental values was found to fit the relationship 1n(theoretical J) = - 3.8 + 5.77 (1/theta) with a regression coefficient of 0.98 and was proposed to be due to one or more of the following parameters: (1) a villus tip to base gradient of transport (influx) activity; (2) a dependence of brush-border influx area on substrate concentration in the bulk incubation media; and (3) an end-product inhibition of the overall transport rate. 6. It is apparent from the data that the flux of glucose across the unstirred layer is ordinarily the rate-limiting step in the trans-brush-border transport of this sugar by hamster jejunum when less than saturating concentrations of glucose are used. At high shaking rates the contribution of the unstirred layer is reduced.