Biomedical subjects

L J Miller

Publications and source records attributed to L J Miller.

At least 163 records · Page 9Linked to original sources

PubMed1990

Physicochemical determinants in hepatic extraction of small peptides.

Although the liver is known to extract amino acids and organic anions by well-characterized transport systems, the factors that regulate the hepatic uptake of small, circulating peptides are poorly understood. We previously reported that cholecystokinin octapeptide, a biologically active form of cholecystokinin, is efficiently cleared by the liver and that uptake depends on its carboxyl-terminal tetrapeptide (Trp-Met-Asp-PheNH2). Here we further define the physicochemical determinants for hepatic clearance of cholecystokinin. A series of 13 tetrapeptides, including eight analogs of the carboxyl-terminal tetrapeptide of cholecystokinin-8 with different charges, hydrophobicity and amino-acid sequences, were prepared by solid-phase synthesis, purified by high-performance liquid chromatography and characterized by amino-acid analysis and mass spectrometry. Radioiodination was performed by oxidative or nonoxidative techniques. Hydrophobicity of individual radiolabeled peptides was calculated using published hydrophobicity data or measured directly by determining their partition between octanol and aqueous triethylammonium acetate. First-pass hepatic extraction of radiolabeled peptides was determined with a nonrecirculating, isolated, perfused rat liver model. First-pass hepatic extraction of injected, labeled peptides varied from 4% to 86% and correlated significantly (r = 0.85; p less than 0.0002) with hydrophobicity. Hydrophobic peptides with positive, neutral or negative charges were avidly extracted (30% to 86%) by the liver; first-pass clearance of hydrophobic peptides with similar charges varied with amino-acid sequence. In contrast, the first-pass hepatic extraction of positively or negatively charged hydrophilic tetrapeptides was negligible (less than 10%). These results suggest that hydrophobicity and amino-acid sequence--but not anionic or cationic nature--are the major determinants of hepatic extraction of cholecystokinin, and perhaps other small, circulating peptides.

Amino Acid Sequence↗

PubMed1990

Lack of metabolic effects of cholecystokinin on hepatocytes.

We previously reported that the liver was the major organ that extracts small, biologically active, circulating forms of cholecystokinin. Although our work indicated extensive degradation of cholecystokinin extracted from plasma during its transit across the hepatocyte, it was unclear whether cholecystokinin might also have a physiological effect on this cell before its intracellular degradation. Therefore we tested the hypothesis that cholecystokinin has a direct biological effect on hepatocytes. Using freshly isolated or cultured hepatocytes, we studied whether cholecystokinin-octapeptide alters protein synthesis, affects amino acid transport or influences cytosolic free calcium concentrations. Using liver slices, we also determined the effect of cholecystokinin-octapeptide on cyclic nucleotide levels. Cholecystokinin-octapeptide, up to a concentration of 1 mumol/L, had no effect on the incorporation of radiolabeled amino acids into total hepatocyte protein; in contrast, comparable molar amounts of insulin stimulated protein synthesis by as much as 37% (ED50 = 1.5 x 10(-10) mol/L). Although insulin and glucagon stimulated the transport into hepatocytes of 14C-alpha-aminoisobutyric acid, a nonmetabolizable amino acid analog, cholecystokinin-octapeptide had no affect Cholecystokinin-octapeptide also did not affect either the concentration of calcium in individual hepatocytes, as measured by digitized video microscopy using Fura-2, or the levels of cyclic AMP or cyclic GMP in liver slices. Our results show that cholecystokinin has no effect on protein synthesis, on amino acid transport or on hepatocyte calcium and cyclic nucleotide levels. These and our previous data suggest that the primary outcome of hepatic extraction of cholecystokinin is hormone degradation.

Amino Acids↗

PubMed1990

GR 38032F (ondansetron), a selective 5HT3 receptor antagonist, slows colonic transit in healthy man.

The newly recognized class of 5-hydroxytryptamine receptors (5HT3) may be involved in the induction of nausea, since their pharmacological antagonists are effective against emesis induced by chemotherapy. 5HT3 receptors are present on enteric neurons, and 5HT3 blockers may produce mild constipation; we thus hypothesized that 5HT3 receptors would modulate colonic motility. To determine if GR 38032F, a selective 5HT3 antagonist known to have antiemetic effects, influences colonic transit in health, a randomized, double-blind, placebo-controlled crossover study was performed. Using a radiopaque marker technique, colonic transit was quantified in 39 healthy volunteers (19 men, 20 nonpregnant women) 18-70 years of age. On a standard 25-g fiber diet, 16 mg of GR 38032F was given orally thrice daily. Gastrointestinal peptides (peptide YY, human pancreatic polypeptide, neurotensin, motilin, gastrin-cholecystokinin, substance P) were also measured in plasma fasting and postprandially. Mean total colonic transit time on placebo was 27.8 hr, while on GR 38032F it was 39.1 hr (P less than 0.0005). Transit times through the left colon (P less than 0.0005) and rectosigmoid (P less than 0.05) were prolonged by the drug, but right colonic transit was not significantly altered. Transit times did not correlate with age or gender, but subjects with shorter transit times were significantly more affected than were those with longer transit times. The peak release of peptide YY was minimally decreased following GR 38032F (P less than 0.01), but the peak and integrated postprandial responses of human pancreatic polypeptide, neurotensin, motilin, gastrin-cholecystokinin, and substance P were not significantly altered by the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1990

Changes in tone of canine gallbladder measured by an electronic pneumatic barostat.

We developed an electronic pneumatic barostat to measure changes in gallbladder muscle tone in vivo independent of biliary flow dynamics. Dogs were prepared with a gallbladder cannula for insertion of barostat balloon and an inflatable balloon-occluder around the cystic duct. The barostat was validated to maintain a constant pressure of 2 +/- 0.4 (SE) mmHg within a plastic balloon of "infinite" compliance that filled the gallbladder lumen; changes in balloon volume reflected changes in wall tone because intraluminal pressure was kept constant. Gallbladder tone, as measured by the barostat balloon volume, varied cyclically with the duodenal migrating motor complex and decreased by 28 +/- 8% (P less than 0.05) at the time of phase III in the stomach and duodenum. Superimposed rapid changes in barostat volume occurred during phase III. The barostat response to motilin mimicked events during spontaneous phase III; in contrast, the response to cholecystokinin octapeptide (CCK-OP) was greater (volume decrease = 53 +/- 12%) and no phasic changes occurred. Two distinct patterns of gallbladder contraction were demonstrated: a basal tone increase with superimposed phasic contractions observed during phase III and after motilin, and a basal tone increase without phasic activity that occurs after CCK-OP.

Animals↗

PubMed1990

Psychotic denial of pregnancy: phenomenology and clinical management.

Psychotic denial of pregnancy in chronic mentally ill women may place the women and their fetuses at high risk of postpartum emotional disturbance, precipitous or unassisted delivery, fetal abuse, and neonaticide. Psychotic denial of pregnancy is illustrated with case reports from an inpatient program for pregnant mentally ill women. Women who denied their pregnancies tended to have a diagnosis of chronic schizophrenia, to have previously lost custody of children, and to anticipate separation from the baby they were carrying. The author suggests that treatment for such patients should take place in a setting that integrates comprehensive psychiatric and obstetrical care and may include pharmacotherapy, supportive psychotherapy, and evaluation of the patient's parenting skills and support network to assess whether she is able to keep her baby.

Adult↗

PubMed1990

The formal treatment contract in the inpatient management of borderline personality disorder.

Formal, written contracts between the patient and the treatment team have been shown to be useful in the inpatient management of borderline personality disorder by fostering a therapeutic alliance, containing dangerous behavior, and protecting the integrity of the treatment. The author discusses the advantages and disadvantages of such contracts and points out several common contractual errors, including making a contract too restrictive, allowing the contract to substitute for psychotherapy, and using the contract as a means of defense or punishment. She provides 12 guidelines, for formulating successful contracts, beginning with the need to clearly state the purpose of the treatment plan mutually agreed on by patient and staff.

Adult↗

PubMed1990

Biochemical characterization of the cholecystokinin receptor on CHP212 human neuroblastoma cells.

Cholecystokinin (CCK) receptors reside on a large number of cell types along the digestive tract and in the nervous system. A human neuroblastoma cell line (CHP212) has recently been described to express a type A receptor, with structural specificity similar to that on pancreatic acinar cells and gall bladder smooth muscle cells but different from the predominant type of binding site found in brain (type B). In this work, we have performed photoaffinity labeling and protease peptide mapping of the CHP212 receptor and have compared it to other type A CCK receptors. 125I-D-Tyr-Gly-[(Nle28,31,pNO2-Phe33)-CCK-26-33], a probe that possesses a photolabile residue at position 33 within the theoretical receptor-binding domain of this hormone, specifically labeled a Mr = 80,000-90,000 glycoprotein on this cell line, while labeling larger proteins (Mr = 85,000-95,000) on rat pancreas and human gall bladder. Deglycosylation with endo-beta-N-acetylglucosaminidase F yielded bands of Mr = 43,000 from CHP212 and gall bladder and Mr = 42,000 from pancreas. Peptide mapping of the deglycosylated bands using Staphylococcus aureus V8 protease demonstrated identical patterns in CHP212 and gall bladder and a similar but different pattern in pancreas. Thus, although possessing heterogeneity in their carbohydrate domains, CCK receptors on human neuroblastoma cells (CHP212) and human gall bladder smooth muscle cells have highly similar or identical protein cores. The core protein on another type A CCK receptor, from rat pancreas, appears to differ from these, likely representing molecular heterogeneity between species.

Affinity Labels↗

PubMed1990

Violent families and the rhetoric of harmony.

Observing that the violent realities of family life belie the social rhetoric of harmony, most sociologists recommend 'demythologizing' the family. This paper challenges that view, arguing that social rhetoric must be analysed rather than debunked. The sense-making activities of actors who engage in violent family events are identified as a strategic site for such an analyses. The paper explores the ways in which the rhetoric of family harmony is routinely sustained and reproduced. Two kinds of supports are considered (i) macrosocial supports, which sustain family rhetoric by integrating it into a wider system of collective representations; and (ii) microsocial supports which sustain family rhetoric by embodying it in the accounts of family members.

Family↗

PubMed1989

Purification and characterization of the rat pancreatic cholecystokinin receptor.

Cholecystokinin (CCK) is a peptide hormone that has a variety of physiologically important functions in the gastrointestinal tract, in which distinct high affinity receptors have been identified. We describe here the purification of the digitonin-solubilized rat pancreatic receptor as an initial step in the determination of its primary structure. Solubilization of total pancreatic membranes using 1% digitonin resulted in a single class of binding sites with a specific content of 4 pmol/mg as measured in a soluble binding assay using the nonpeptidyl CCK antagonist [3H]3S[-]-N-[2,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-1,4- benzodiazepine-3-yl]-1H-indole-2-carboxamide [( 3H]364,718). The solubilized receptor was purified using the following chromatographic steps: 1) cation exchange; 2) Ulex europaeus agglutinin-I-agarose; and 3) Sephacryl S-300. The final preparation of the purified receptor had a specific content of 8,055 pmol/mg, which represented a 9,051-fold purification from intact membranes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the purified receptor preparation under reducing conditions resulted in a predominant polypeptide with an Mr = 85,000-95,000 and minor polypeptides of Mr = 57,000 and 26,000 as determined by radiolabeling and silver staining. Solubilized pancreatic membranes were affinity labeled with the peptidyl CCK agonist 125I-D-Tyr-Gly-[(Nle28,31,6-NO2-Phe33)CCK-26-33] and chromatographed under conditions similar to those described for untreated membranes. Elution of radioactive peaks from each chromatographic column was coincident with [3H]364,718 binding activity and resulted in a labeled polypeptide having the same electrophoretic mobility as receptor derived from freshly labeled membranes and purified from untreated membranes. High performance liquid-gel exclusion chromatography of the crude digitonin-solubilized membrane preparation revealed an estimated molecular size for the [3H]364,718-binding activity of 370,000, which was consistent with the size determined by nondenaturing gel electrophoresis of the purified receptor complexed with the labeled nonpeptidyl antagonist. Binding of [3H]364,718 to the purified receptor preparation was comparable to that observed with the crude solubilized pancreatic membrane preparation; and both the homologous ligand 364,718 (Ki = 0.5 nm) and CCK-8 (Ki = 1.4 microM) competed for binding to both preparations in a similar manner.

Animals↗

PubMed1989

Protease peptide mapping of affinity-labeled rat pancreatic cholecystokinin-binding proteins.

Affinity-labeling probes with sites of cross-linking distributed along the ligand have been used to biochemically characterize the pancreatic cholecystokinin (CCK) receptor. Probes with photolabile sites spanning the receptor-binding domain have labeled a Mr = 85,000-95,000 plasma membrane protein, while a probe cross-linked via the amino terminus of CCK-33, far removed from the carboxyl-terminal receptor-binding domain, has labeled a distinct Mr = 80,000 protein. In this work, protease peptide mapping of the pancreatic proteins labeled by each of these probes has been performed to gain insight into the identities of the bands and to define domains of the labeled proteins. Photolabile decapeptide probes with sites of cross-linking at the amino terminus, mid region, and carboxyl terminus of the receptor-binding domain each labeled a Mr = 85,000-95,000 glycoprotein with a Mr = 42,000 core protein and similar Staphylococcus aureus V8 protease peptide maps. This confirms that each probe labels the same binding protein and the same domain of that protein. Serial slices through the broad labeled band were separately deglycosylated and protease-treated, demonstrating a single protein core with differential glycosylation. The CCK-33-based probe, however, labeled predominantly two proteins, one having similar sizes in its native and deglycosylated forms to that labeled by the decapeptide probes and a distinct Mr = 80,000 protein. Of note, the peptide map of the protein believed to be the same as that labeled by the shorter probes was different, suggesting that this probe labeled the binding subunit at a site distinct from that which was labeled by the short probes.

Affinity Labels↗

PubMed1989

Use of a nitrotryptophan-containing peptide for photoaffinity labeling the pancreatic cholecystokinin receptor.

We report the preparation and characterization of a new type of intrinsic photoaffinity labeling probe, on the basis of the incorporation of a photolabile nitrotryptophan into a biologically relevant domain of a peptide. The model system used was the pancreatic cholecystokinin (CCK) receptor, previously affinity labeled with a variety of probes. Those studies have suggested that an Mr = 85,000-95,000 protein is more likely to be labeled as the site of covalent attachment approaches the receptor-binding domain of this hormone. Indeed, CCK has a Trp in the center of its receptor-binding region, and replacement of that residue with 6-nitrotryptophan resulted in a photolabile probe which affinity labeled the same Mr = 85,000-95,000 pancreatic membrane protein. This probe, 125I-D-Tyr-Gly-[(Nle28,31,6-NO2-Trp30)CCK-26-33], was synthesized by solid-phase and solution techniques and characterized by mass spectrometry. Following oxidative iodination, it was purified on HPLC to 2000 Ci/mmol. Binding to pancreatic membranes was rapid, temperature dependent, reversible, saturable, and specific and was with high affinity (Kd = 3 nM). While its binding affinity was only 3-fold lower than that of native CCK-8, this probe was 70-fold less potent than native hormone in stimulating amylase secretion (EC50 = 1 nM) and equally efficacious to native hormone. Despite the slight decrease in affinity, this probe demonstrated a high relative efficiency of covalent labeling of the Mr = 85,000-95,000 protein. This confirms that the Mr = 85,000-95,000 protein represents the hormone-binding subunit of the CCK receptor and demonstrates the utility of this type of photoaffinity labeling probe.(ABSTRACT TRUNCATED AT 250 WORDS)

Affinity Labels↗

PubMed1989

Effect of selective 5HT3 antagonist (GR 38032F) on small intestinal transit and release of gastrointestinal peptides.

Antagonists of 5-hydroxytryptamine type 3 (5HT3) receptors reduce the nausea induced by cisplatinum, but the effects of these agents on 5HT3 receptors in the human gut remain to be defined. We examined the actions of one of these drugs (Glaxo GR 38032F) on small intestinal transit and mouth-to-cecum transit times in healthy man. We also quantified its effects on the release of peptide YY (PYY), neurotensin, human pancreatic polypeptide, gastrin-cholecystokinin, and motilin. Ten healthy volunteers were enrolled in a randomized, double-blind, placebo-controlled crossover study. Following a single intravenous dose of GR 38032F (0.15 mg/kg), we measured the time to appearance in plasma of sulfapyridine after injection of salicylazosulfapyridine into the duodenum. This was used as a measure of duodenocecal transit. The appearance of hydrogen in breath after ingestion of a meal containing lactulose was also correspondingly used to quantify the mouth-to-cecum transit of the "head" of the meal. Gastrointestinal hormones were assayed in plasma by specific RIAs; samples were drawn fasting (10 min after injection) and after breakfast (358 calories: 15.7 g protein, 55.4 g carbohydrate, 8.1 g fat). The postprandial integrated response and peak release of PYY was decreased by GR 38032F. There was also a trend for the peak release of neurotensin to be reduced. GR 38032F did not significantly alter small intestinal transit times or mouth-to-cecum transit times. We conclude that GR 38032F does not have a major effect on small intestinal transit in health.

Adult↗

PubMed1989

Culture of human neoplastic gastrointestinal smooth muscle cells.

Due to limited growth potential of primary cultures and the absence of continuous lines of healthy enteric smooth muscle, we have studied the culture behavior of neoplastic gastrointestinal smooth muscle cells. Forty-six human enteric smooth muscle neoplasms (leiomyomas and leiomyosarcomas) were studied while fresh and/or after culture in vitro and growth in vivo in athymic nude mice, with assessments made of morphology, growth characteristics, and biochemical markers of differentiation. The state of differentiation of the tumors varied, with well-differentiated tumors tending to express binding sites for the gastrointestinal hormone cholecystokinin, whereas less well-differentiated tumors did not. Poorly differentiated tumors were the easiest to establish in culture in vitro and to grow in vivo in nude mice. When the cells placed directly into culture proliferated to confluent density, they underwent morphologic differentiation from a spread, fibroblastlike shape to a slender spindle morphology, with these cells possessing fewer biosynthetic organelles and arranging themselves in characteristic "hill and valley" arrays. However, the highly differentiated characteristics of expression of desmin or cholecystokinin-binding sites were not observed in cultured cells. In contrast, cells that had been passaged in nude mice before culture displayed a proliferative phenotype and failed to undergo morphologic differentiation on reaching confluent density. Four human enteric smooth muscle cell lines (documented by chromosomal analysis) originating in stomach, jejunum, ileum, and rectum were established using this strategy.

Cholecystokinin↗

PubMed1989

Functional and biochemical characterization of the human gallbladder muscularis cholecystokinin receptor.

Gallbladders removed at cholecystectomy are a potentially useful source of human receptor for the gastrointestinal peptide hormone cholecystokinin (CCK). Seven healthy gallbladders (removed incidentally at time of resection of hepatic metastases) and 50 diseased gallbladders were studied. Cholecystokinin radioligand binding to an enriched plasma membrane preparation from these tissues was shown to be rapid, reversible, temperature-dependent, saturable, specific, and high-affinity. Computer analysis of equilibrium binding data using the Ligand program best fit a single class of binding sites with Kd = 1.0 +/- 0.1 nM (mean +/- SEM). This was similar in health and disease, with no apparent differences related to age, gender, or body habitus. The structural specificity for binding to this site correlated well with relative potencies for CCK-gastrin peptides to stimulate gallbladder contraction. To biochemically characterize this receptor, we used a battery of reagents, including "long" (125I-Bolton Hunter-CCK-33) and "short" 125I-D-Try-Gly-[(Nle28,31)CCK-26-33] probes that were cross-linkable through their amino terminus and a monofunctional probe with a photolabile group at its carboxyl terminus 125I-D-Tyr-Gly[(Nle28,31,pNO2-Phe33)CCK-26-33]. All probes specifically labeled a human gallbladder muscularis protein of Mr = 85,000-95,000, which was also independent of diagnosis. Labeling of this band was inhibited in a concentration-dependent manner by CCK-8 and by L-364,718. Thus, the CCK receptor present on the very common surgically removed human gallbladder is functionally and biochemically intact and is useful for further characterization.

Adult↗

PubMed1989

Serotoninergic activity stimulates melanin dispersion within dermal melanophores of newts.

Systemic injections of 5-hydroxytryptophan (5-HTP), the precursor to serotonin, stimulates melanin dispersion within dermal melanophores of red-spotted newts (Notophthalmus viridescens). Injections of para-Chlorophenylalanine (PCPA), an inhibitor of serotonin synthesis, inhibited melanin dispersion, and hence darkening of the skin, when newts were transferred to a dark background. The results indicate a role for serotoninergic activity in the background adaptation response in this amphibian.

5-Hydroxytryptophan↗

PubMed1989

Elbow extension in the C5 quadriplegic using functional neuromuscular stimulation.

A system has been designed to provide overhead reach in C5/6 quadriplegic subjects using functional neuromuscular stimulation (FNS) for control of the triceps muscle. The system uses the position of the arm in space as the input command, relieving the user from having to supply a conscious command signal. By measuring the position of the arm, the magnitude of the gravitational and passive torques opposing elbow extension can be calculated. This torque is counteracted by electrical activation of the triceps muscle, with the appropriate stimulus parameters determined from the recruitment characteristics of each electrode. Sufficient stimulus is applied to produce full elbow extension. Intermediate elbow angles are achieved using voluntary elbow flexor torque to counteract the effects of the stimulation. System performance was tested in two subjects. Subjects were asked to reach targets with and without stimulation, with loads up to 500 g in the hand. Using the FNS system, subjects were able to successfully reach the target positions above the horizontal that were inaccessible without stimulation.

Elbow Joint↗

PubMed1989

Structural analysis of a distinct subtype of CCK receptor on human gastric smooth muscle tumors.

Human gastric smooth muscle tumors (leiomyosarcomas) have been shown to express cholecystokinin (CCK) binding sites that are functionally similar to physiologically important receptors present on their cells of origin. In this work, we have applied affinity-labeling techniques using 125I-D-Tyr-Gly-[Nle28,31]CCK-(26-33) to attempt to define the ligand-binding subunit of this receptor, and we have used the receptor antagonist L364,718 and deglycosylating enzymes to compare this molecule with well-defined CCK receptors on the classical peripheral targets (pancreas and gallbladder) of this hormone. To validate the use of 125I-D-Tyr-Gly-[Nle28,31]CCK-(26-33) for this tissue, we demonstrated that it bound to leiomyosarcoma membranes in a rapid, reversible, saturable, specific, and high-affinity manner (Kd = 0.8 nM). Although previous affinity labeling of this tissue with a CCK-33-based probe identified multiple bands, only one of those candidate proteins was predominantly labeled in the present work (Mr 100,000) by using a probe that is cross-linked through a site in greater proximity to the receptor-binding domain. Labeling was inhibited in a concentration-dependent manner by CCK-8 but not by structurally unrelated ligands. Although endo-beta-N-acetyl-glucosaminidase F digestion shifted this band by Mr 5,000, demonstrating that it was a glycoprotein, the deglycosylation product was very different from other CCK receptors studied. Also, unlike pancreatic and gallbladder CCK receptors, affinity labeling of this receptor was not affected by L364,718. These observations confirm that the gastric smooth muscle tumor CCK receptor represents a receptor subtype that is distinct from other peripheral CCK receptors, biochemically as well as functionally.

Adult↗

PubMed1989

Processing of cholecystokinin by isolated liver cells.

Although hepatic uptake of cholecystokinin (CCK) has been demonstrated, the liver cell involved and the mechanism of uptake remain unclear. We have used dispersed rat hepatocytes, Kupffer cells, and hepatic endothelial cells to characterize uptake and metabolism of radiolabeled CCK peptides. Only rat hepatocytes showed significant uptake of 125I-labeled cholecystokinin octapeptide (125I-CCK-8). Peptide specificity of uptake by hepatocytes was similar to that seen in the isolated perfused rat liver, with extraction of 125I-CCK-8 being sevenfold greater than that of 125I-CCK-33. Uptake was saturable, as 10(-4) M CCK-4 inhibited uptake of 125I-CCK-8 by 85%. Uptake was rapid, temperature dependent, and extensive and was decreased by metabolic inhibition, a proteolytic enzyme (trypsin), organic anions (sulfobromophthalein and taurocholic acid), and an inhibitor of anion transport 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. In addition, uptake was dependent on extracellular anions but not on extracellular sodium, calcium, or magnesium. After uptake, hepatocytes released radiolabel in a time- and temperature-dependent manner, predominantly in metabolized forms. Thus the hepatocyte is the liver cell that extracts CCK by an active, anion-dependent process. The characteristics of the uptake process resemble those described for organic anions and small, cyclic peptides and suggest that small, linear peptides may undergo hepatocyte extraction by a similar mechanism.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗