Comparison of Liver Function, Emotional Status, and Quality of Life of Living Liver Donors in Taiwan.

BACKGROUND: Living donor liver transplantation may put the donor at risk of physical and psychological impacts. Recovery of physical and psychological function as well as quality of life (QOL) in living liver donors warrants investigation. OBJECTIVES: This study aims to examine the recovery of liver function, emotional status, and QOL in living liver donors through a comparison with the general population and reference values. METHODS: This descriptive, comparative study included 97 living liver donors who underwent surgery from 2008 to 2012 and were divided into 4 groups according to their postoperative period (1 year [n = 31], 2 years [n = 31], 3 years [n = 21], and 4 years above [n = 14]). Data were collected retrospectively in a medical center in northern Taiwan. RESULTS: The mean aspartate aminotransferase level was 20.2-32.1 U/L, the mean alanine aminotransferase level was 14.7-33.5 U/L, and the mean total bilirubin level was 10.8-15.5 µmol/L among the 4 groups. Among donors of the 4 groups, 23.8%-51.6% and 0%-29% were defined as having a mild level of anxiety and depression, respectively. Donors in the 1- and 2-year groups had poorer QOL in the physical function, role physical, vitality, and mental health domains than did the general population of Taiwan (P < .05). CONCLUSIONS: Liver function was at normal levels in all 4 groups. The emotional and psychological function of living liver donors should be monitored and health-related QOL should be promoted during the first and second year after liver donation.

Reconstitution of lysosomal sulfate transport in proteoliposomes.

As part of a strategy to purify the lysosomal sulfate transporter, we developed a method for reconstitution of transport in artificial membrane vesicles. Lysosomal membranes were prepared from Percoll density gradient purified rat liver lysosomes and membrane proteins were solubilized using the non-ionic detergent, Triton X-100. The solubilized proteins were mixed with liposomes prepared by sonication of egg yolk lecithin and the detergent was removed by passage of the mixture over Bio-beads XAD2. The resulting proteoliposomes exhibited saturable sulfate transport with characteristics that were very similar to those observed in lysosomal membranes. Transport in proteoliposomes had a Km of 155 microM, exhibited pH dependence and was sensitive to inhibition by DIDS. Reconstitution of transport in proteoliposomes may be useful as an assay for purification of the lysosomal sulfate carrier.

Lysosomal sulfate transport: inhibitor studies.

Sulfate derived from the degradation of macromolecules is released from lysosomes via a carrier mediated process. In order to further characterize this process, recognized inhibitors of the erythrocyte band 3 anion transporter were examined for their effects on the lysosomal system. Studies with band 3 transport site inhibitors such as DIDS, SITS and phenylglyoxal indicated that, similar to the case for the band 3 protein, the lysosomal transporter has critical lysine and arginine residues. Band 3 translocation pathway or channel blocking inhibitors had mixed effects on the lysosomal system. 1,2-Cyclohexanedione, which covalently modifies a band 3 arginine residue distinct from that modified by phenylglyoxal, inhibited lysosomal sulfate transport. In contrast, the potent band 3 inhibitor dipyridamole had no effect on lysosomal sulfate transport indicating that there are some structural differences between the erythrocyte and lysosomal anion transporters. The band 3 translocation inhibitors niflumic acid and dinitrofluorobenzene were both effective inhibitors of the lysosomal system. Cupric ion inhibited sulfate transport while Ca2+, Co2+, Mg2+, Mn2+, and Zn2+ had no inhibitory effects. Exposure of intact lysosomes to trypsin largely ablated transport of sulfate. This information should be useful in efforts to further elucidate the structure and function of the lysosomal sulfate transporter.

Pulsatile insulin secretion in isolated rat islets.

The pancreas secretes insulin in an oscillatory fashion, but the precise site of the pacemaker for pulsatile insulin secretion has not been identified. These studies were designed to determine whether islets also secrete insulin in a pulsatile fashion if they are isolated from their pancreatic milieu. Isolated rat islets (80-100) were perifused 8 h in culture medium after overnight incubation, and samples were collected at 3.3-min intervals. Insulin secretion was evaluated for pulsatility with the Clifton Cycle Detection Program. Perifusion of islets was associated with a spontaneous, persistent, and regular pulsatility of insulin secretion, which was observed in all conditions tested. Perifusion with medium containing 5.5 mM glucose (n = 11) demonstrated oscillations with a mean periodicity of 17.6 +/- 1.1 min and a mean amplitude of 4.8 +/- 0.4 microU/ml when overall mean insulin concentration was 16.7 +/- 2.4 microU/ml. When the glucose concentration was 16.7 mM (n = 9), overall mean insulin concentration was 54.4 +/- 2.6 microU/ml, with increases in periodicity (22.0 +/- 1.3 min) and amplitude (10.7 +/- 0.5 microU/ml). All measurements were significantly different from those observed during perifusion with 5.5 mM glucose (P less than 0.02-0.001). Theophylline (1 mM) also enhanced the overall mean insulin concentration and amplitude (69.4 +/- 10.4 and 14.2 +/- 1.2 microU/ml, respectively) compared with control studies without theophylline (16.7 +/- 5.3 and 4.3 +/- 0.5 microU/ml) (P less than 0.01). The period of the cycle was also increased from 17.5 +/- 1.1 to 26.4 +/- 6.3 min, but this was not significantly different from the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Sustained pulsatile insulin secretion from adenomatous human beta-cells. Synchronous cycling of insulin, C-peptide, and proinsulin.

The endocrine pancreas secretes insulin in a pulsatile fashion. This rhythm is generated at a site within the pancreas, although its precise location has not been determined. With an in vitro system, we tested the possibility that beta-cells might generate spontaneous pulsatile insulin secretion in the absence of any external influence. Human insulinoma tissue from five patients was perifused for 7-10 h with RPMI-1640 medium and constant concentrations of glucose (5.5 mM). Insulin, C-peptide, and proinsulin were measured in the effluent collected at 3.3-min intervals. All three peptides demonstrated pulsatility of secretion in a similar, synchronous fashion that was sustained throughout each study. The Clifton cycle detection program demonstrated cycling in all five tumors, with an average period for all tumors of 28, 29, and 26 min for insulin, C-peptide, and proinsulin, respectively. Spectral analysis confirmed the regularity and consistency of the hormonal secretory patterns. Mean hormone concentrations secreted by different tumors varied, but insulin and C-peptide were secreted in a nearly 1:1 ratio. This study demonstrates 1) that beta-cells are able to generate spontaneous pulsatile insulin secretory activity, which is independent of innervation or the presence of other islet cells, and 2) proinsulin secretion from the beta-cell also has an inherent pulsatility. The synchrony observed in the cycles of proinsulin and its peptide products confirms their common secretory pathway in the beta-cell. We conclude that the beta-cell may be the originator of insulin cycling.

Erratic oscillatory characteristics of plasma insulin concentrations in patients with insulinoma: mechanism for unpredictable hypoglycemia.

Patients with insulin-producing tumors may have hypoglycemic symptoms at unpredictable times. This study evaluated whether plasma insulin oscillations, known to occur in normal individuals but not explored in patients with insulinomas, could be an underlying mechanism for such events. Nine normal subjects and five patients with proven insulinomas were studied in the fasting state. Serial sampling of arterialized blood over 80-100 min, at 2- or 3-min intervals was performed. In normal subjects, mean plasma glucose and insulin concentrations were 5.3 +/- 0.1 mmol/L and 58 +/- 9 pmol/L, respectively. Regular, low-amplitude plasma insulin oscillations were observed, with a period of 10-17 min. The subjects with insulinomas had lower mean plasma glucose and higher insulin concentrations than controls, 3.6 +/- 0.3 mmol/L (P = 0.01) and 150 +/- 42 pmol/L (P = 0.01), respectively. They also had insulin oscillations that appeared unstable as a result of variability in duration and amplitude compared with controls. The insulin pulses were irregular, and interpeak intervals varied between 4-54 min in different subjects; in some subjects, the amplitude was also variable, with sudden spontaneous pulses as high as 565 pmol/L, with an associated glucose decrement. We conclude that large spontaneous bursts of insulin secretion occur in patients with insulinomas as part of an erratic pattern of oscillatory insulin secretion, and these can account for unpredictable occurrences of hypoglycemia.

Luteinizing hormone releasing activity of [Gln8]-LHRH and [His5, Trp7, Tyr8]-LHRH in the cockerel, in vivo and in vitro.

The luteinizing hormone (LH)-releasing activity of two distinct chicken luteinizing hormone releasing hormones ([Gln8]-LHRH and [His5, Trp7, Tyr8]-LHRH) were evaluated in white Leghorn cockerels. In the first study, thirty birds were randomly allotted to five groups and injected, i.v., with 0.9% saline, [Gln8]-LHRH (cLHRH I, 1 microM or 10 microM) or [His5, Trp7, Tyr8]-LHRH, (cLHRH II; 1 microM or 10 microM). Blood samples were drawn prior to and through 60 min following the injection, and plasma was collected for LH determination. In the second study, anterior pituitary cells from cockerels were dispersed and preincubated for 1 hr. Approximately 1.5 X 10(5) cells per tube were incubated with either Medium 199 buffer (control), 8-bromo-cAMP or various doses of cLHRH I or cLHRH II at final concentrations ranging from 0.02 to 100.0 nM. At the end of a two hour incubation, supernatant was collected and the concentration of LH determined. Injection of cLHRH I or cLHRH II at 1 microM and 10 microM levels caused a significant increase in blood LH concentrations which peaked 5 min following injection. There were, however, no differences between the stimulatory effect of cLHRH I compared to cLHRH II at either dose. On the other hand, cLHRH II was found to be 4.7 times more potent than cLHRH I in stimulating LH release from dispersed pituitary cells. It is suggested that cLHRH II may have greater affinity for the gonadotroph receptor, greater uptake by the cell, and/or that it may be more resistant to in vitro degradation than cLHRH I. On the other hand, an extra pituitary site of degradation may be more effective in metabolizing cLHRH II, resulting in its equipotency with cLHRH I, in vivo.

Oscillations of circulating plasma insulin concentrations in the rat.

In previous studies, we found that insulin is secreted in a pulsatile fashion in vitro in isolated rat pancreatic islets. This study evaluated whether similar plasma insulin fluctuations occur in the rat in vivo. Freely moving rats were implanted with a chronic jugular catheter and serial blood samples were obtained 48-72 hrs post surgery. Blood was sampled at 3 min intervals for 60 mins with volume replacement using a red cell preparation. Plasma insulin concentrations were observed to fluctuate around a mean of 10.6 +/- 1.1 uU/ml, with an amplitude of 4.7 +/- 0.5 uU/ml and a period of 13.3 +/- 1 mins (n = 6). This was similar to the cycling observed in isolated islets at similar glucose concentrations. Sampling during the dark phase of the light-dark cycle in the rat was associated with an increase in the mean plasma level, amplitude and period of insulin oscillations compared with values obtained during the light phase (n = 3). These data are the first in vivo demonstration of oscillatory circulating insulin concentrations in the rat and show that the pulsatility in this species is similar to that observed in other mammals including man. We conclude that the chronically catheterised rat is a useful model for the evaluation of oscillating insulin concentrations in vivo, and may provide interesting insights by comparison with in vitro data in the same species.

Influence of age, strain, and beta-adrenergic agonist on insulin sensitivity in chicks as determined by an adaptation of the euglycemic clamp technique.

The euglycemic clamp technique has been widely used to examine changes in in vivo insulin sensitivity during physiological changes in mammals. The technique offers the advantage that the tissue uptake of glucose induced by a set dose of insulin is determined at the normal (steady state) circulating concentration of glucose (euglycemia). The euglycemic clamp technique has been modified to examine in vivo sensitivity to insulin in chickens. Insulin sensitivity is determined by the rate of infusion of exogenous glucose required to maintain euglycemia. Young (6 to 8-wk-old) male chickens (White Leghorn) are more sensitive to insulin than adult males of the same strain. There is, however, no difference in insulin sensitivity between young male chicks of broiler and White Leghorn strains. Chronic administration of beta-adrenergic agonist (L-640,033, donated by Merck, Sharp, and Dohme Research Laboratories, Rahway, NJ) in the diet, at levels of 0, .25, 1.0, and 4.0 ppm for 3 to 5 days also did not influence in vivo insulin sensitivity.

Luteinizing hormone secretion from anterior pituitary cells of the cockerel: evidence for an ultradian rhythm.

Studies were conducted to characterize the secretory pattern of luteinizing hormone (LH) from perfused anterior pituitary cells of the cockerel in the presence and absence of secretagogues. Basal LH secretion was found to occur in a rhythmic pattern, with the mean cycle period for 5 different perfusion columns estimated to be 66.4 +/- 4.0 min. By contrast, when cells were repeatedly exposed to luteinizing hormone-releasing hormone (LHRH) at 90-min intervals, the period of the LH rhythm was altered to approximate the interval of LHRH pulses (96.7 +/- 6.1 min; n = 3 perfusion columns). Exposure of cells to media containing 50 mM potassium chloride (KCl) augmented the release of LH and slightly decreased the cycle period compared to that which occurs during basal secretion (49.2 min) but did not eliminate the rhythm. Finally, perifusion of cells with medium containing 10 microM colchicine eliminated the rhythm of secretion. These data suggest that there exists an ultradian rhythm of LH secretion from the chicken pituitary which is expressed in the absence of hypothalamic input and is modified by the hypothalamic releasing factor, LHRH. In addition, the rhythm does not seem to be affected in the short-term by a small depolarization of the membrane as occurs with the addition of KCl to the perifusion media but does seem to be dependent upon microtubule function.

Factors determining social function of patients after renal transplantation in Taiwan.

BACKGROUND: Patients who are no longer in need of dialysis as a consequence save time and reduce stress every day. Social function was an important issue in patients with successful renal transplantation. According Bandura's social cognitive theory, ones' behavior is affected by social context and affective factors continuously. The quality of social function needs further investigation. PURPOSE: The aims of this study were to describe the degree of social function after renal transplantation and to explore its predictive factors. METHOD: A cross-sectional and descriptive study design was conducted in the outpatient department of a medical center in northern Taiwan from July to October 2010. The recipients were a convenience sample of 101 participants who had undergone renal transplantation. Hierarchical multivariate regression analysis was used to explore the predictive factors related to social function. RESULTS: The results showed that renal transplant recipients have moderate to high social function. Regression analyses showed that psychological factors (perceived stress, stress after renal transplantation, and depressive symptoms) and social participation (paid-work and leisure activity) explained 37.1% of the total variance for social function. Depressive symptoms explained most of the total variance. CONCLUSION: After renal transplantation, patients experienced higher levels of social function. Perceived stress, stress after renal transplantation, depressive symptoms, paid-work, and leisure activity were the predictive factors of social function. Managing levels of depressive symptoms is highly recommended to elevate the patient's social function.

Association between use of FK506 and prevalence of post-transplantation diabetes mellitus in kidney transplant patients.

BACKGROUND: Tacrolimus (FK506) use has been suggested as a risk factor for post-transplantation diabetes mellitus (PTDM) because it can impair insulin secretion. This association warrants further investigation. This study aimed to examine the prevalence of PTDM and its association with FK506 use in kidney transplant recipients. The study also aimed to examine the relationship of FK506 use and diabetes-related biologic markers. METHODS: A retrospective chart review was used to collect data at a medical center in northern Taiwan from September 2003 to February 2012. PTDM was defined with the use of the criteria of the American Diabetes Association. RESULTS: Among 166 patients included in the analysis, PTDM was reported in 49 patients (29.5%). A total of 93 patients used the FK506 regimen, of whom 34 (36.6%) were PTDM cases. Logistic regression showed that FK506 use (odds ratio [OR], 2.71; 95% confidence interval [CI], 1.20-6.11; P = .016) and older age (OR,1.08; 95% CI, 1.03-1.13; P = .001) were significant risk factors for PTDM. In addition, FK506 use in PTDM cases was associated with a significantly higher hemoglobin A1c level (7.55 vs 5.81; P = .01) and a borderline significantly higher insulin resistance index (3.24 vs 1.92; P = .053) than was FK506 use without the presence of PTDM. CONCLUSIONS: Older age and an FK506 regimen were important predictors of the prevalence of PTDM. Greater early detection and prevention efforts for PTDM are needed for older transplant recipients. PTDM patients with an FK506 regimen had higher hemoglobin A1c levels and insulin resistance index than did patients who did not use FK506. The association of serum indicators with FK506 use in the prevalence of PTDM warrants further investigation.

Effect of gangliosides on primary and secondary plaque-forming cells responses and on suppressor T-cells induction.

This study was designed to determine the suppressive effect of bovine brain gangliosides on primary and secondary anti-sheep red blood cell (SRBC) plaque-forming cells (PFC) response. Spleen cells from inbred C57BL/6J mice were used as sources of lymphocytes. The result showed that levels of gangliosides at 50 and 100 micrograms/ml suppressed primary anti-SRBC PFC responses about 30% and 60%, respectively, of normal control. In contrast, secondary anti-SRBC PFC were not suppressed by the same levels of gangliosides. Likewise, PFC response from mixing SRBC-primed T-cells with naive B-cells was not suppressed by gangliosides. In addition, induction of suppressor T-cells was reduced by 50 and 100 micrograms/ml of gangliosides, 57% and 63%, respectively, versus 86% of suppression of PFC response by the control suppressor T-cells. These results further suggest the role of gangliosides as immunomodulators.

Oscillations of lactate released from islets of Langerhans: evidence for oscillatory glycolysis in beta-cells.

Oscillations in the glycolytic process have been demonstrated in a number of different biological systems. However, their presence has never been demonstrated in insulin-secreting beta-cells. We used lactate as a marker for glycolysis and measured lactate and insulin concentrations in the effluent of isolated perifused rat islets of Langerhans. Sustained regular oscillations in lactate concentrations with an average period of 16-20 min were observed in islets that were perifused with medium containing 5.5 or 16.7 mM glucose. Sustained oscillations of insulin concentrations secreted by the islets were also observed in these experiments, and the average period of oscillation was 14.6 +/- 2.3 min at 16.7 mM glucose. Mean insulin concentrations at 5.5 mM glucose were too low to permit analysis of oscillations. Spectral analysis confirmed the regularity of the lactate and insulin oscillations and showed peaks that were consistent with the average periods obtained using the Clifton program. Moreover, spectral analysis demonstrated marked similarity between the patterns of lactate and insulin oscillation during perifusion with 16.7 mM glucose. Cross-correlation analysis found these oscillations not to be consistently in phase. In conclusion, sustained oscillations in lactate released from islets of Langerhans suggest that the glycolytic process in beta-cells also oscillates. The similarity of the periods of lactate and insulin raises the possibility that oscillations in glycolysis may provide a mechanism for pulsatile insulin secretion.

Evidence for pancreatic pacemaker for insulin oscillations in low-frequency range.

Circulating insulin concentrations oscillate in regular fashion, with periods that fall into a high-frequency (period of 5-17 min) or low-frequency (period of 50-150 min) range. Only the high-frequency oscillations have so far been reported in vitro, suggesting that these derive from a primary pancreatic source. This study tested whether the low-frequency insulin oscillations could also be identified in vitro. Rat islets of Langerhans were perifused for 20 h using RPMI medium with 5.5 mM glucose. Perifusate fractions were collected at 9.9-min intervals. Mean insulin concentrations at the outset were 21.4 +/- 2.9 microU/ml, increased to 32.5 +/- 4.6 (P < 0.05) between 13 and 17 h after the start of perifusion, and then either leveled off or decreased to baseline. Superimposed on this general trend, we found sustained insulin oscillations with a period of 50-100 min. The mean amplitude was 14.2 +/- 4.2 microU/ml, and the amplitude/mean ratio was 64.6 +/- 12%. Spectral analysis revealed significant peaks at periods that were close to either 50 or 100 min and a smaller peak at 24-37 min. These data, using in vitro methodology and constant glucose concentrations, indicate the presence of sustained, spontaneous, low-frequency, ultradian insulin oscillations in the pancreatic islets. This provides evidence for a pancreatic component that may participate in the previously described in vivo ultradian insulin oscillations. This finding may also provide a mechanism for the apparent escape from glucose entrainment of serum insulin oscillations in non-insulin-dependent diabetes mellitus.

Regulation of lysosomal sulfate transport by thyroid hormone.

Sulfate transport was examined in rat liver lysosomes that were isolated from thyroid hormone-treated, thyroidectomized, and control animals. Sulfate uptake was significantly decreased in lysosomes from animals that had received intraperitoneal T3 (3,5,3'-triiodothyronine) at a dose of 20 micrograms/100 g body weight. The effect of T3 was maximal by 24 h post-injection and resulted in marked decreases in both Vmax (control: 155 +/- 33 pmol/unit of beta-hexosaminidase/30 s versus T3 treated: 24 +/- 7 pmol/unit of beta-hexosaminidase/30 s) and Km (control: 213 +/- 34 microM versus T3 treated: 92 +/- 6 microM). Thyroidectomy was associated with a significant increase in Vmax (control: 250 pmol/unit of beta-hexosaminidase/30 s versus thyroidectomized: 564 pmol/unit of beta-hexosaminidase/30 s), while Km was not significantly affected. The effect of thyroid hormone on lysosomal sulfate transport appeared to be relatively specific. In contrast to its effect on sulfate transport, T3 treatment had no effect on the uptake of either glucose or N-acetylglucosamine by rat liver lysosomes. Lysosomal pH, acidification in response to Mg/ATP, and the specific activities of alpha-L-iduronidase, beta-hexosaminidase, beta-D-glucosidase, and acid phosphatase were unaffected by T3 administration. Incubation of T3 with lysosomes from control animals had little or no effect on sulfate transport. Treatment of isolated lysosomes with either protein kinase A or alkaline phosphatase resulted in modest stimulation of transport. Thus, T3 does not appear to regulate transport by either direct interaction with the lysosomal transporter or protein kinase A-mediated phosphorylation. The exact mechanism for the inhibitory effect of T3 on lysosomal sulfate transport remains to be determined.

A mathematical model of oscillatory insulin secretion.

Insulin is secreted in sustained oscillatory fashion from isolated islets of Langerhans. This finding has led to the assumption of an underlying synchronizing process that coordinates insulin oscillations. This assumption was tested by developing a mathematical model of oscillatory insulin secretion in which we included degree of synchrony as a parameter. We first evaluated insulin oscillations in perifused isolated rat islets, using spectral analysis to determine their regularity and frequency. A parsimonious mathematical model was developed to account for these characteristics. The model postulates a group of secretory units discharging at discrete intervals with the same underlying period. Variation from two sources, phase differences between units (synchrony) and regularity within units, is introduced by adding two normally distributed random variables with standard deviations (Sg and Si, respectively) to the secretory period. Sets of 100 simulations for different values of Sg and Si were run. Results of the simulations suggest that the system tolerates a relatively large degree of asynchrony yet still demonstrates regularity of oscillations on spectral analysis. Comparison with perifusion data suggests that a moderate degree of asynchrony between islets can best account for the pattern of insulin oscillations observed. This model provides a theoretical basis for the study of mechanisms for insulin oscillations.

Lysosomal sulphate transport is dependent upon sulphydryl groups.

Using thiol blocking agents, we examined the role of sulphydryl groups for function of the lysosomal sulphate transport system. Monothiol binding reagents, p-hydroxymercuribenzoic acid (p-HMB) and p-chloromercuribenzene sulphonic acid (p-CMBS), dithiol binding reagents such as CuCl2, the alkylating agent, N-ethylmaleimide (NEM), and NADH all inhibited lysosomal sulphate transport. The inhibitory effects of NEM and Cu2+ were not additive, suggesting that they both act upon the same critical sulphydryl group(s). Unlike the case for NEM, the inhibitory effects of Cu2+ were reversed by the reducing agent, dithiothreitol. Exposure to NEM resulted in a seven-fold increase in Km to 867 microM versus a control value of 126 microM and a modest decrease in Vmax to 99 pmolperunit beta-hexosaminidase per 30 s versus a control value of 129 pmolperunit beta-hexosaminidase per 30 s. Similar although somewhat less dramatic results were obtained using Cu2+ with an increase of Km to 448 microM and a Vmax of 77 pmolperunit beta-hexosaminidase per 30 s. The sulphate transport activity of detergent solubilized lysosomal membranes could be bound to a p-chloromercuribenzoic acid (p-CMB)-Sepharose sulphydryl affinity resin and eluted with mercaptoethanol. Sulphydryl groups thus appear to play a role in sulphate transport through effects on substrate affinity. Sulphydryl-binding appears to be a strategy that may be useful for purification of the transporter.

ATP stimulates lysosomal sulphate transport at neutral pH: evidence for phosphorylation of the lysosomal sulphate carrier.

ATP markedly stimulated sulphate uptake by rat liver lysosomes that had been treated with N-ethylmaleimide to block the effects of the lysosomal proton-translocating ATPase (H+-ATPase). Maximal stimulation required millimolar concentrations of ATP and neutral buffer pH. ATP-stimulated transport exhibited saturation kinetics with a Km of 175 microM, identical with the Km for lysosomal sulphate uptake at pH 5.0, a process that does not require ATP. The requirement for ATP was specific: other nucleotides such as AMP, ADP, CTP, GTP, ITP and UTP failed to stimulate transport. Adenosine 5'-[beta,gamma-imido]triphosphate, the non-hydrolysable analogue of ATP, also failed to stimulate sulphate uptake, suggesting a requirement for ATP hydrolysis. Lysosomal pH, membrane potential and glucose transport were unchanged by the presence of ATP under the experimental conditions, consistent with a direct effect of ATP on the sulphate transporter. Exposure of lysosomes to protein kinase A and protein kinase C inhibitors did not alter the stimulation of sulphate transport by ATP. The lysosomal sulphate transport protein might be subject to regulation by a phosphorylation pathway that is not dependent on protein kinase A or protein kinase C.